Two proteins of Aequorea victoria were molecularly engineered and produced in mammalian cells, in... more Two proteins of Aequorea victoria were molecularly engineered and produced in mammalian cells, in order to serve as specific reporters of subcellular microenvironments. Aequorin (AEQ), a Ca(2+)-sensitive photoprotein, was successfully targeted to three intracellular locations: cytosol, nucleus and mitochondria. The recombinant apoprotein, reconstituted into active AEQ by the addition of the prosthetic group to the culture medium, allows the direct measurement of [Ca2+] within those compartments, thus directly addressing questions of large biological interest. The same approach was utilized for the green fluorescent protein (GFP) for specific labelling, in vivo, of the various subcellular structures. GFP was targeted to mitochondria: the recombinant protein, strongly fluorescent in a highly reducing environment, provides a powerful tool for visualizing these organelles in living cells, and may represent the prototype of a new family of intracellularly targeted fluorescent probes.
Calcium concentration must be finely tuned in all eukaryotic cells to ensure the correct performa... more Calcium concentration must be finely tuned in all eukaryotic cells to ensure the correct performance of its signalling function. Neuronal activity is exquisitely dependent on the control of Ca2+ homeostasis: its alterations ultimately play a pivotal role in the origin and progression of many neurodegenerative processes. A complex toolkit of Ca2+ pumps and exchangers maintains the fluctuation of cytosolic Ca2+ concentration within the appropriate threshold. Two ubiquitous (isoforms 1 and 4) and two neuronally enriched (isoforms 2 and 3) of the plasma membrane Ca2+ATPase (PMCA pump) selectively regulate cytosolic Ca2+ transients by shaping the sub-plasma membrane (PM) microdomains. In humans, genetic mutations in ATP2B1, ATP2B2 and ATP2B3 gene have been linked with hearing loss, cerebellar ataxia and global neurodevelopmental delay: all of them were found to impair pump activity. Here we report three additional mutations in ATP2B3 gene corresponding to E1081Q, R1133Q and R696H amino a...
Endoplasmic reticulum (ER)–mitochondria contact sites are critical structures for cellular functi... more Endoplasmic reticulum (ER)–mitochondria contact sites are critical structures for cellular function. They are implicated in a plethora of cellular processes, including Ca2+ signalling and mitophagy, the selective degradation of damaged mitochondria. Phosphatase and tensin homolog (PTEN)-induced kinase (PINK) and Parkin proteins, whose mutations are associated with familial forms of Parkinson’s disease, are two of the best characterized mitophagy players. They accumulate at ER–mitochondria contact sites and modulate organelles crosstalk. Alterations in ER–mitochondria tethering are a common hallmark of many neurodegenerative diseases including Parkinson’s disease. Here, we summarize the current knowledge on the involvement of PINK1 and Parkin at the ER–mitochondria contact sites and their role in the modulation of Ca2+ signalling and mitophagy.
Parkinson’s disease (PD), the second most common neurodegenerative disorder, is characterized by ... more Parkinson’s disease (PD), the second most common neurodegenerative disorder, is characterized by dopaminergic neuronal loss that initiates in the substantia nigra pars compacta and by the formation of intracellular inclusions mainly constituted by aberrant α-synuclein (α-syn) deposits known as Lewy bodies. Most cases of PD are sporadic, but about 10% are familial, among them those caused by mutations in SNCA gene have an autosomal dominant transmission. SNCA encodes α-syn, a small 140-amino acids protein that, under physiological conditions, is mainly localized at the presynaptic terminals. It is prevalently cytosolic, but its presence has been reported in the nucleus, in the mitochondria and, more recently, in the mitochondria-associated ER membranes (MAMs). Whether different cellular localizations may reflect specific α-syn activities is presently unclear and its action at mitochondrial level is still a matter of debate. Mounting evidence supports a role for α-syn in several mitoc...
The mitochondrion is the major energy source within the cell that regulates different cellular pr... more The mitochondrion is the major energy source within the cell that regulates different cellular processes. In addition to this important function the mitochondrion also houses its own DNA and protein synthesizing machinery. Human mtDNA is circular, has 16596 base pairs and encodes 13 polypeptides of the oxidative phosphorylation complex (OXPHOS) that are localized to the mitochondrial inner membrane, 22 transfer RNAs and 2 ribosomal RNAs (12S and 16S rRNAs) for mitochondrial translation. It is inherited maternally (although evidence for partial paternal inheritance has recently been described) and commonly used to establish maternal family ties. Mutations in mtDNA, which are 100-fold higher than nuclear DNA, were created by travel and mixing and are linked to disease and aging.
Casignals regulate most aspects of animal cell life. They are of particular importance to the ner... more Casignals regulate most aspects of animal cell life. They are of particular importance to the nervous system, in which they regulate specific functions, from neuronal development to synaptic plasticity. The homeostasis of cell Camust thus be very precisely regulated: in all cells Capumps transport it from the cytosol to the extracellular medium (the Plasma Membrane CaATPases, hereafter referred to as PMCA pumps) or to the lumen of intracellular organelles (the Sarco/Endoplasmatic Reticulum CaATPase and the Secretory Pathway CaATPase, hereafter referred to as SERCA and SPCA pumps, respectively). In neurons and other excitable cells a powerful plasma membrane Na/Caexchanger (NCX) also exports Cafrom cells. Quantitatively, the PMCA pumps are of minor importance to the bulk regulation of neuronal Ca. However, they are important in the regulation of Cain specific sub-plasma membrane microdomains which contain a number of enzymes that are relevant to neuronal function. The PMCA pumps (of ...
Ion channels play an important role in the regulation of organelle function within the cell, as p... more Ion channels play an important role in the regulation of organelle function within the cell, as proven by increasing evidence pointing to a link between altered function of intracellular ion channels and different pathologies ranging from cancer to neurodegenerative diseases, ischemic damage, and lysosomal storage diseases. Recent Advances: A link between these pathologies and redox state as well as lipid homeostasis and ion channel function is in the focus of current research. Ion channels are target of modulation by lipids and lipid messengers, although in most cases the mechanistic details have not been clarified yet. Ion channel function importantly impacts production of reactive oxygen species (ROS), especially in the case of mitochondria and lysosomes. ROS, in turn, may modulate the function of intracellular channels triggering thereby a feedback control under physiological conditions. If produced in excess, ROS can be harmful to lipids and may produce oxidized forms of these membrane constituents that ultimately affect ion channel function by triggering a "circulus vitiosus." The present review summarizes our current knowledge about the contribution of intracellular channels to oxidative stress and gives examples of how these channels are modulated by lipids and how this modulation may affect ROS production in ROS-related diseases. Future studies need to address the importance of the regulation of intracellular ion channels and related oxidative stress by lipids in various physiological and pathological contexts. Antioxid. Redox Signal. 00, 000-000.
Biochemical and Biophysical Research Communications, 2017
The plasma membrane Ca 2þ ATPase (PMCA pump) is a member of the superfamily of P-type pumps. It i... more The plasma membrane Ca 2þ ATPase (PMCA pump) is a member of the superfamily of P-type pumps. It is organized in the plasma membrane with ten transmembrane helices and two main cytosolic loops, one of which contains the catalytic center. It also contains a long C-terminal tail that houses the binding site for calmodulin, the main regulator of the activity of the pump. The pump also contains a number of other regulators, among them acidic phospholipids, kinases, and numerous protein interactors. Separate genes code for 4 basic pump isoforms in mammals, additional isoform complexity being generated by the alternative splicing of primary transcripts. Pumps 1 and 4 are expressed ubiquitously, pumps 2 and 3 are tissue restricted, with preference for the nervous system. In essentially all cells, the pump coexists with much more powerful systems that clear Ca 2þ from the cytosol, e.g. the SERCA pump and the Na þ /Ca 2þ exchanger. Its role in the global regulation of cellular Ca 2þ homeostasis is thus quantitatively marginal: its main function is the regulation of Ca 2þ signaling in selected sub-plasma membrane microdomains where Ca 2þ modulated interactors also reside. Malfunctions of the pump linked to genetic mutations are now described with increasing frequency, the disease phenotypes being especially severe in the nervous system where isoforms 2 and 3 predominate. The analysis of the pump defects suggests that the disease phenotypes are likely to be related to the imperfect modulation of Ca 2þ signaling in selected sub-plasma membrane microdomains, leading to the defective control of the activity of important Ca 2þ dependent interactors.
Alpha-synuclein (α-syn) is an abundant neuronal protein whose physiological function, even if sti... more Alpha-synuclein (α-syn) is an abundant neuronal protein whose physiological function, even if still not completely understood, has been consistently related to synaptic function and vesicle trafficking. A group of disorders known as synucleinopathies, among which Parkinson’s disease (PD), is deeply associated with the misfolding and aggregation of α-syn, which can give rise to proteinaceous inclusion known as Lewy bodies (LB). Proteostasis stress is a relevant aspect in these diseases and, currently, the presence of oligomeric α-syn species rather than insoluble aggregated forms, appeared to be associated with cytotoxicity. Many observations suggest that α-syn is responsible for neurodegeneration by interfering with multiple signaling pathways. α-syn protein can directly form plasma membrane channels or modify with their activity, thus altering membrane permeability to ions, abnormally associate with mitochondria and cause mitochondrial dysfunction (i.e. mitochondrial depolarization...
Huntington disease (HD) is caused by the CAG (Q) expansion in exon 1 of the IT15 gene encoding a ... more Huntington disease (HD) is caused by the CAG (Q) expansion in exon 1 of the IT15 gene encoding a polyglutamine (poly-Q) stretch of the Huntingtin protein (Htt). In the wild type protein, the repeats specify a stretch of up 34 Q in the N-terminal portion of Htt. In the pathological protein (mHtt) the poly-Q tract is longer. Proteolytic cleavage of the protein liberates an N-terminal fragment containing the expanded poly-Q tract becomes harmful to cells, in particular to striatal neurons. The fragments cause the transcriptional dysfunction of genes that are essential for neuronal survival. Htt, however, could also have non-transcriptional effects, e.g. it could directly alter Ca2+ homeostasis and/or mitochondrial morphology and function. Ca2+ dyshomeostasis and mitochondrial dysfunction are considered important in the molecular aetiology of the disease. Here we have analyzed the effect of the overexpression of Htt fragments (18Q, wild type form, wtHtt and 150Q mutated form, mHtt) on C...
The photoprotein aequorin generates blue light upon binding of Ca(2+) ions. Together with its ver... more The photoprotein aequorin generates blue light upon binding of Ca(2+) ions. Together with its very low Ca(2+)-buffering capacity and the possibility to add specific targeting sequences, this property has rendered aequorin particularly suitable to monitor Ca(2+) concentrations in specific subcellular compartments. Recently, a new generation of genetically encoded Ca(2+) probes has been developed by fusing Ca(2+)-responsive elements with the green fluorescent protein (GFP). Aequorin has also been employed to this aim, resulting in an aequorin-GFP chimera with the Ca(2+) sensitivity of aequorin and the fluorescent properties of GFP. This setup has actually solved the major limitation of aequorin, for example, its poor ability to emit light, which rendered it inappropriate for the monitoring of Ca(2+) waves at the single-cell level by imaging. In spite of the numerous genetically encoded Ca(2+) indicators that are currently available, aequorin-based probes remain the method of election ...
Advances in Experimental Medicine and Biology, 2011
Mitochondria play a central role in cell biology, not only as producers of ATP but also as regula... more Mitochondria play a central role in cell biology, not only as producers of ATP but also as regulators of the Ca(2+) signal. The translocation by respiratory chain protein complexes of H(+) across the ion-impermeable inner membrane generates a very large H(+) electrochemical gradient that can be employed not only by the H(+) ATPase to run the endoergonic reaction of ADP phosphorylation, but also to accumulate cations into the matrix. Mitochondria can rapidly take up Ca(2+) through an electrogenic pathway, the uniporter, that acts to equilibrate Ca(2+) with its electrochemical gradient, and thus accumulates the cation into the matrix, and they can release it through two exchangers (with H(+) and Na(+), mostly expressed in non-excitable and excitable cells, respectively), that utilize the electrochemical gradient of the monovalent cations to prevent the attainment of electrical equilibrium.The uniporter, due to its low Ca(2+) affinity, demands high local Ca(2+) concentrations to work. In different cell systems these high Ca(2+) concentration microdomains are generated, upon cell stimulation, in proximity of the plasma membrane and the sarco/endoplasmic reticulum Ca(2+) channels.Recent work has revealed the central role of mitochondria in signal transduction pathways: evidence is accumulating that, by taking up Ca(2+), they not only modulate mitochondrial activities but also tune the cytosolic Ca(2+) signals and their related functions. This review analyses recent developments in the area of mitochondrial Ca(2+) signalling and attempts to summarize cell physiology aspects of the mitochondrial Ca(2+) transport machinery.
Plasma membrane Ca2+-adenosine triphosphatases (ATPases) (PMCAs) are high-affinity calcium pumps ... more Plasma membrane Ca2+-adenosine triphosphatases (ATPases) (PMCAs) are high-affinity calcium pumps that contribute to the maintenance of intracellular Ca2+ homeostasis by exporting Ca2+ from the cytosol to the extracellular environment. Mammals have four genes, encoding the proteins PMCA1 through PMCA4. Each gene transcript is alternatively spliced to generate several variants. Their distribution is tissue and cell specific and undergoes regulation during cell development and differentiation. Traditionally, these pumps have been considered to play a housekeeping role in controlling basal Ca2+ levels but more recently it became clear that the presence (and the co-expression) of different isoforms must be related to a more specialized function. Only one of the four genes (that encodes PMCA2) has been causally linked to disease in mammals: several spontaneous mutations are responsible for hereditary deafness and balance impairment. Other complex human disease phenotypes such as cancer, cardiac dysfunction, and infertility are likely to be associated with PMCA function but no direct link with its mutations has been reported so far.
Two proteins of Aequorea victoria were molecularly engineered and produced in mammalian cells, in... more Two proteins of Aequorea victoria were molecularly engineered and produced in mammalian cells, in order to serve as specific reporters of subcellular microenvironments. Aequorin (AEQ), a Ca(2+)-sensitive photoprotein, was successfully targeted to three intracellular locations: cytosol, nucleus and mitochondria. The recombinant apoprotein, reconstituted into active AEQ by the addition of the prosthetic group to the culture medium, allows the direct measurement of [Ca2+] within those compartments, thus directly addressing questions of large biological interest. The same approach was utilized for the green fluorescent protein (GFP) for specific labelling, in vivo, of the various subcellular structures. GFP was targeted to mitochondria: the recombinant protein, strongly fluorescent in a highly reducing environment, provides a powerful tool for visualizing these organelles in living cells, and may represent the prototype of a new family of intracellularly targeted fluorescent probes.
Calcium concentration must be finely tuned in all eukaryotic cells to ensure the correct performa... more Calcium concentration must be finely tuned in all eukaryotic cells to ensure the correct performance of its signalling function. Neuronal activity is exquisitely dependent on the control of Ca2+ homeostasis: its alterations ultimately play a pivotal role in the origin and progression of many neurodegenerative processes. A complex toolkit of Ca2+ pumps and exchangers maintains the fluctuation of cytosolic Ca2+ concentration within the appropriate threshold. Two ubiquitous (isoforms 1 and 4) and two neuronally enriched (isoforms 2 and 3) of the plasma membrane Ca2+ATPase (PMCA pump) selectively regulate cytosolic Ca2+ transients by shaping the sub-plasma membrane (PM) microdomains. In humans, genetic mutations in ATP2B1, ATP2B2 and ATP2B3 gene have been linked with hearing loss, cerebellar ataxia and global neurodevelopmental delay: all of them were found to impair pump activity. Here we report three additional mutations in ATP2B3 gene corresponding to E1081Q, R1133Q and R696H amino a...
Endoplasmic reticulum (ER)–mitochondria contact sites are critical structures for cellular functi... more Endoplasmic reticulum (ER)–mitochondria contact sites are critical structures for cellular function. They are implicated in a plethora of cellular processes, including Ca2+ signalling and mitophagy, the selective degradation of damaged mitochondria. Phosphatase and tensin homolog (PTEN)-induced kinase (PINK) and Parkin proteins, whose mutations are associated with familial forms of Parkinson’s disease, are two of the best characterized mitophagy players. They accumulate at ER–mitochondria contact sites and modulate organelles crosstalk. Alterations in ER–mitochondria tethering are a common hallmark of many neurodegenerative diseases including Parkinson’s disease. Here, we summarize the current knowledge on the involvement of PINK1 and Parkin at the ER–mitochondria contact sites and their role in the modulation of Ca2+ signalling and mitophagy.
Parkinson’s disease (PD), the second most common neurodegenerative disorder, is characterized by ... more Parkinson’s disease (PD), the second most common neurodegenerative disorder, is characterized by dopaminergic neuronal loss that initiates in the substantia nigra pars compacta and by the formation of intracellular inclusions mainly constituted by aberrant α-synuclein (α-syn) deposits known as Lewy bodies. Most cases of PD are sporadic, but about 10% are familial, among them those caused by mutations in SNCA gene have an autosomal dominant transmission. SNCA encodes α-syn, a small 140-amino acids protein that, under physiological conditions, is mainly localized at the presynaptic terminals. It is prevalently cytosolic, but its presence has been reported in the nucleus, in the mitochondria and, more recently, in the mitochondria-associated ER membranes (MAMs). Whether different cellular localizations may reflect specific α-syn activities is presently unclear and its action at mitochondrial level is still a matter of debate. Mounting evidence supports a role for α-syn in several mitoc...
The mitochondrion is the major energy source within the cell that regulates different cellular pr... more The mitochondrion is the major energy source within the cell that regulates different cellular processes. In addition to this important function the mitochondrion also houses its own DNA and protein synthesizing machinery. Human mtDNA is circular, has 16596 base pairs and encodes 13 polypeptides of the oxidative phosphorylation complex (OXPHOS) that are localized to the mitochondrial inner membrane, 22 transfer RNAs and 2 ribosomal RNAs (12S and 16S rRNAs) for mitochondrial translation. It is inherited maternally (although evidence for partial paternal inheritance has recently been described) and commonly used to establish maternal family ties. Mutations in mtDNA, which are 100-fold higher than nuclear DNA, were created by travel and mixing and are linked to disease and aging.
Casignals regulate most aspects of animal cell life. They are of particular importance to the ner... more Casignals regulate most aspects of animal cell life. They are of particular importance to the nervous system, in which they regulate specific functions, from neuronal development to synaptic plasticity. The homeostasis of cell Camust thus be very precisely regulated: in all cells Capumps transport it from the cytosol to the extracellular medium (the Plasma Membrane CaATPases, hereafter referred to as PMCA pumps) or to the lumen of intracellular organelles (the Sarco/Endoplasmatic Reticulum CaATPase and the Secretory Pathway CaATPase, hereafter referred to as SERCA and SPCA pumps, respectively). In neurons and other excitable cells a powerful plasma membrane Na/Caexchanger (NCX) also exports Cafrom cells. Quantitatively, the PMCA pumps are of minor importance to the bulk regulation of neuronal Ca. However, they are important in the regulation of Cain specific sub-plasma membrane microdomains which contain a number of enzymes that are relevant to neuronal function. The PMCA pumps (of ...
Ion channels play an important role in the regulation of organelle function within the cell, as p... more Ion channels play an important role in the regulation of organelle function within the cell, as proven by increasing evidence pointing to a link between altered function of intracellular ion channels and different pathologies ranging from cancer to neurodegenerative diseases, ischemic damage, and lysosomal storage diseases. Recent Advances: A link between these pathologies and redox state as well as lipid homeostasis and ion channel function is in the focus of current research. Ion channels are target of modulation by lipids and lipid messengers, although in most cases the mechanistic details have not been clarified yet. Ion channel function importantly impacts production of reactive oxygen species (ROS), especially in the case of mitochondria and lysosomes. ROS, in turn, may modulate the function of intracellular channels triggering thereby a feedback control under physiological conditions. If produced in excess, ROS can be harmful to lipids and may produce oxidized forms of these membrane constituents that ultimately affect ion channel function by triggering a "circulus vitiosus." The present review summarizes our current knowledge about the contribution of intracellular channels to oxidative stress and gives examples of how these channels are modulated by lipids and how this modulation may affect ROS production in ROS-related diseases. Future studies need to address the importance of the regulation of intracellular ion channels and related oxidative stress by lipids in various physiological and pathological contexts. Antioxid. Redox Signal. 00, 000-000.
Biochemical and Biophysical Research Communications, 2017
The plasma membrane Ca 2þ ATPase (PMCA pump) is a member of the superfamily of P-type pumps. It i... more The plasma membrane Ca 2þ ATPase (PMCA pump) is a member of the superfamily of P-type pumps. It is organized in the plasma membrane with ten transmembrane helices and two main cytosolic loops, one of which contains the catalytic center. It also contains a long C-terminal tail that houses the binding site for calmodulin, the main regulator of the activity of the pump. The pump also contains a number of other regulators, among them acidic phospholipids, kinases, and numerous protein interactors. Separate genes code for 4 basic pump isoforms in mammals, additional isoform complexity being generated by the alternative splicing of primary transcripts. Pumps 1 and 4 are expressed ubiquitously, pumps 2 and 3 are tissue restricted, with preference for the nervous system. In essentially all cells, the pump coexists with much more powerful systems that clear Ca 2þ from the cytosol, e.g. the SERCA pump and the Na þ /Ca 2þ exchanger. Its role in the global regulation of cellular Ca 2þ homeostasis is thus quantitatively marginal: its main function is the regulation of Ca 2þ signaling in selected sub-plasma membrane microdomains where Ca 2þ modulated interactors also reside. Malfunctions of the pump linked to genetic mutations are now described with increasing frequency, the disease phenotypes being especially severe in the nervous system where isoforms 2 and 3 predominate. The analysis of the pump defects suggests that the disease phenotypes are likely to be related to the imperfect modulation of Ca 2þ signaling in selected sub-plasma membrane microdomains, leading to the defective control of the activity of important Ca 2þ dependent interactors.
Alpha-synuclein (α-syn) is an abundant neuronal protein whose physiological function, even if sti... more Alpha-synuclein (α-syn) is an abundant neuronal protein whose physiological function, even if still not completely understood, has been consistently related to synaptic function and vesicle trafficking. A group of disorders known as synucleinopathies, among which Parkinson’s disease (PD), is deeply associated with the misfolding and aggregation of α-syn, which can give rise to proteinaceous inclusion known as Lewy bodies (LB). Proteostasis stress is a relevant aspect in these diseases and, currently, the presence of oligomeric α-syn species rather than insoluble aggregated forms, appeared to be associated with cytotoxicity. Many observations suggest that α-syn is responsible for neurodegeneration by interfering with multiple signaling pathways. α-syn protein can directly form plasma membrane channels or modify with their activity, thus altering membrane permeability to ions, abnormally associate with mitochondria and cause mitochondrial dysfunction (i.e. mitochondrial depolarization...
Huntington disease (HD) is caused by the CAG (Q) expansion in exon 1 of the IT15 gene encoding a ... more Huntington disease (HD) is caused by the CAG (Q) expansion in exon 1 of the IT15 gene encoding a polyglutamine (poly-Q) stretch of the Huntingtin protein (Htt). In the wild type protein, the repeats specify a stretch of up 34 Q in the N-terminal portion of Htt. In the pathological protein (mHtt) the poly-Q tract is longer. Proteolytic cleavage of the protein liberates an N-terminal fragment containing the expanded poly-Q tract becomes harmful to cells, in particular to striatal neurons. The fragments cause the transcriptional dysfunction of genes that are essential for neuronal survival. Htt, however, could also have non-transcriptional effects, e.g. it could directly alter Ca2+ homeostasis and/or mitochondrial morphology and function. Ca2+ dyshomeostasis and mitochondrial dysfunction are considered important in the molecular aetiology of the disease. Here we have analyzed the effect of the overexpression of Htt fragments (18Q, wild type form, wtHtt and 150Q mutated form, mHtt) on C...
The photoprotein aequorin generates blue light upon binding of Ca(2+) ions. Together with its ver... more The photoprotein aequorin generates blue light upon binding of Ca(2+) ions. Together with its very low Ca(2+)-buffering capacity and the possibility to add specific targeting sequences, this property has rendered aequorin particularly suitable to monitor Ca(2+) concentrations in specific subcellular compartments. Recently, a new generation of genetically encoded Ca(2+) probes has been developed by fusing Ca(2+)-responsive elements with the green fluorescent protein (GFP). Aequorin has also been employed to this aim, resulting in an aequorin-GFP chimera with the Ca(2+) sensitivity of aequorin and the fluorescent properties of GFP. This setup has actually solved the major limitation of aequorin, for example, its poor ability to emit light, which rendered it inappropriate for the monitoring of Ca(2+) waves at the single-cell level by imaging. In spite of the numerous genetically encoded Ca(2+) indicators that are currently available, aequorin-based probes remain the method of election ...
Advances in Experimental Medicine and Biology, 2011
Mitochondria play a central role in cell biology, not only as producers of ATP but also as regula... more Mitochondria play a central role in cell biology, not only as producers of ATP but also as regulators of the Ca(2+) signal. The translocation by respiratory chain protein complexes of H(+) across the ion-impermeable inner membrane generates a very large H(+) electrochemical gradient that can be employed not only by the H(+) ATPase to run the endoergonic reaction of ADP phosphorylation, but also to accumulate cations into the matrix. Mitochondria can rapidly take up Ca(2+) through an electrogenic pathway, the uniporter, that acts to equilibrate Ca(2+) with its electrochemical gradient, and thus accumulates the cation into the matrix, and they can release it through two exchangers (with H(+) and Na(+), mostly expressed in non-excitable and excitable cells, respectively), that utilize the electrochemical gradient of the monovalent cations to prevent the attainment of electrical equilibrium.The uniporter, due to its low Ca(2+) affinity, demands high local Ca(2+) concentrations to work. In different cell systems these high Ca(2+) concentration microdomains are generated, upon cell stimulation, in proximity of the plasma membrane and the sarco/endoplasmic reticulum Ca(2+) channels.Recent work has revealed the central role of mitochondria in signal transduction pathways: evidence is accumulating that, by taking up Ca(2+), they not only modulate mitochondrial activities but also tune the cytosolic Ca(2+) signals and their related functions. This review analyses recent developments in the area of mitochondrial Ca(2+) signalling and attempts to summarize cell physiology aspects of the mitochondrial Ca(2+) transport machinery.
Plasma membrane Ca2+-adenosine triphosphatases (ATPases) (PMCAs) are high-affinity calcium pumps ... more Plasma membrane Ca2+-adenosine triphosphatases (ATPases) (PMCAs) are high-affinity calcium pumps that contribute to the maintenance of intracellular Ca2+ homeostasis by exporting Ca2+ from the cytosol to the extracellular environment. Mammals have four genes, encoding the proteins PMCA1 through PMCA4. Each gene transcript is alternatively spliced to generate several variants. Their distribution is tissue and cell specific and undergoes regulation during cell development and differentiation. Traditionally, these pumps have been considered to play a housekeeping role in controlling basal Ca2+ levels but more recently it became clear that the presence (and the co-expression) of different isoforms must be related to a more specialized function. Only one of the four genes (that encodes PMCA2) has been causally linked to disease in mammals: several spontaneous mutations are responsible for hereditary deafness and balance impairment. Other complex human disease phenotypes such as cancer, cardiac dysfunction, and infertility are likely to be associated with PMCA function but no direct link with its mutations has been reported so far.
Uploads
Papers by Marisa Brini