Papers by Marco Pirazzini
Cells
Skeletal muscle is the most abundant tissue in the body and requires high levels of energy to fun... more Skeletal muscle is the most abundant tissue in the body and requires high levels of energy to function properly. Skeletal muscle allows voluntary movement and body posture, which require different types of fiber, innervation, energy, and metabolism. Here, we summarize the contribution received at the time of publication of this Introductory Issue for the Special Issue dedicated to “Skeletal Muscle Atrophy: Mechanisms at a Cellular Level”. The Special Issue is divided into three sections. The first is dedicated to skeletal muscle pathophysiology, the second to disease mechanisms, and the third to therapeutic development.
International Journal of Molecular Sciences
Tetanus and Botulinum type B neurotoxins are bacterial metalloproteases that specifically cleave ... more Tetanus and Botulinum type B neurotoxins are bacterial metalloproteases that specifically cleave the vesicle-associated membrane protein VAMP at an identical peptide bond, resulting in inhibition of neuroexocytosis. The minute amounts of these neurotoxins commonly used in experimental animals are not detectable, nor is detection of their VAMP substrate sensitive enough. The immune detection of the cleaved substrate is much more sensitive, as we have previously shown for botulinum neurotoxin type A. Here, we describe the production in rabbit of a polyclonal antibody raised versus a peptide encompassing the 13 residues C-terminal with respect to the neurotoxin cleavage site. The antibody was affinity purified and found to recognize, with high specificity and selectivity, the novel N-terminus of VAMP that becomes exposed after cleavage by tetanus toxin and botulinum toxin type B. This antibody recognizes the neoepitope not only in native and denatured VAMP but also in cultured neurons ...
Botulinum Toxin Treatment in Surgery, Dentistry, and Veterinary Medicine, 2020
International Journal of Molecular Sciences, 2022
We used α-Latrotoxin (α-LTx), the main neurotoxic component of the black widow spider venom, whic... more We used α-Latrotoxin (α-LTx), the main neurotoxic component of the black widow spider venom, which causes degeneration of the neuromuscular junction (NMJ) followed by a rapid and complete regeneration, as a molecular tool to identify by RNA transcriptomics factors contributing to the structural and functional recovery of the NMJ. We found that Urocortin 2 (UCN2), a neuropeptide involved in the stress response, is rapidly expressed at the NMJ after acute damage and that inhibition of CRHR2, the specific receptor of UCN2, delays neuromuscular transmission rescue. Experiments in neuronal cultures show that CRHR2 localises at the axonal tips of growing spinal motor neurons and that its expression inversely correlates with synaptic maturation. Moreover, exogenous UCN2 enhances the growth of axonal sprouts in cultured neurons in a CRHR2-dependent manner, pointing to a role of the UCN2-CRHR2 axis in the regulation of axonal growth and synaptogenesis. Consistently, exogenous administration ...
Polyglutamine (polyQ)-expanded androgen receptor (AR) causes spinobulbar muscular atrophy. Skelet... more Polyglutamine (polyQ)-expanded androgen receptor (AR) causes spinobulbar muscular atrophy. Skeletal muscle is a primary site of polyQ-expanded AR toxicity, however it remains to be established what the early pathological processes are and how they unfold during disease progression. Using transgenic, knock-in SBMA mice and patient-derived muscle biopsies, we show that polyQ-expanded AR alters the generation of intrinsic muscle force prior to denervation. The pattern of expression of genes encoding key components of the excitation-contraction coupling (ECC) machinery is altered in the muscles of presymptomatic mice and patients. Altered mitochondrial respiration is another early event followed by stimulus-dependent accumulation of calcium into mitochondria during disease onset and structural organization alterations of the muscle triad. Surgical castration and AR silencing prevented early pathological processes. These observations show that androgen-dependent deregulations of ECC and ...
Abstract: Botulinum neurotoxins (BoNTs) and some animal neurotoxins (β-Bungarotoxin, β-Btx, from ... more Abstract: Botulinum neurotoxins (BoNTs) and some animal neurotoxins (β-Bungarotoxin, β-Btx, from elapid snakes andα-Latrotoxin, α-Ltx, from black widow spiders) are pre-synaptic neurotoxins that paralyse motor axon terminals with similar clinical outcomes in patients. However, their mechanism of action is different, leading to a largely-different duration of neuromuscular junction (NMJ) blockade. BoNTs induce a long-lasting paralysis without nerve terminal degeneration acting via proteolytic cleavage of SNARE proteins, whereas animal neurotoxins cause an acute and complete degeneration of motor axon terminals, followed by a rapid recovery. In this study, the injection of animal neurotoxins in mice muscles previously paralyzed by BoNT/A or /B accelerates the recovery of neurotransmission, as assessed by electrophysiology and morphological analysis. This result provides a proof of principle that, by causing the complete degeneration, reabsorption, and regeneration of a paralysed nerve...
Journal of Neurochemistry, 2021
Abbreviations: ASE, axonal signaling endosomes; BoNT, botulinum neurotoxin; GFP, green fluorescen... more Abbreviations: ASE, axonal signaling endosomes; BoNT, botulinum neurotoxin; GFP, green fluorescent protein; H, heavy chain of tetanus neurotoxin; HC, the 50 kDa carboxy-terminal fragment C of tetanus neurotoxin; HCC, the 25 kDa C-terminal part of HC; HCN, the 25 kDa N-terminal part of fragment C of tetanus neurotoxin; In-In, inhibitory interneurons; L, light chain of tetanus neurotoxins; PFT, pore-forming toxin; PSG, poly-sialoganglioside; TeNT, tetanus neurotoxin; VAMP, vesicle-associated membrane protein.
EMBO Molecular Medicine, 2017
The neuromuscular junction has retained through evolution the capacity to regenerate after damage... more The neuromuscular junction has retained through evolution the capacity to regenerate after damage, but little is known on the inter-cellular signals involved in its functional recovery from trauma, autoimmune attacks, or neurotoxins. We report here that CXCL12a, also abbreviated as stromal-derived factor-1 (SDF-1), is produced specifically by perisynaptic Schwann cells following motor axon terminal degeneration induced by a-latrotoxin. CXCL12a acts via binding to the neuronal CXCR4 receptor. A CXCL12a-neutralizing antibody or a specific CXCR4 inhibitor strongly delays recovery from motor neuron degeneration in vivo. Recombinant CXCL12a in vivo accelerates neurotransmission rescue upon damage and very effectively stimulates the axon growth of spinal cord motor neurons in vitro. These findings indicate that the CXCL12a-CXCR4 axis plays an important role in the regeneration of the neuromuscular junction after motor axon injury. The present results have important implications in the effort to find therapeutics and protocols to improve recovery of function after different forms of motor axon terminal damage.
American Journal of Physiology - Cell Physiology, 2017
We investigated the effects of S1P3 deficiency on the age-related atrophy, decline in force, and ... more We investigated the effects of S1P3 deficiency on the age-related atrophy, decline in force, and regenerative capacity of soleus muscle from 23-mo-old male (old) mice. Compared with muscle from 5-mo-old (adult) mice, soleus mass and muscle fiber cross-sectional area (CSA) in old wild-type mice were reduced by ~26% and 24%, respectively. By contrast, the mass and fiber CSA of soleus muscle in old S1P3-null mice were comparable to those of adult muscle. Moreover, in soleus muscle of wild-type mice, twitch and tetanic tensions diminished from adulthood to old age. A slowing of contractile properties was also observed in soleus from old wild-type mice. In S1P3-null mice, neither force nor the contractile properties of soleus changed during aging. We also evaluated the regenerative capacity of soleus in old S1P3-null mice by stimulating muscle regeneration through myotoxic injury. After 10 days of regeneration, the mean fiber CSA of soleus in old wild-type mice was significantly smaller ...
Expert Opinion on Drug Discovery, 2017
ABSTRACT Introduction: Botulinum neurotoxins (BoNTs) are the most potent toxins known. BoNTs are ... more ABSTRACT Introduction: Botulinum neurotoxins (BoNTs) are the most potent toxins known. BoNTs are responsible for botulism, a deadly neuroparalytic syndrome caused by the inactivation of neurotransmitter release at peripheral nerve terminals. Thanks to their specificity and potency, BoNTs are both considered potential bio-weapons and therapeutics of choice for a variety of medical syndromes. Several variants of BoNTs have been identified with individual biological properties and little antigenic relation. This expands greatly the potential of BoNTs as therapeutics but poses a major safety problem, increasing the need for finding appropriate antidotes. Areas covered: The authors describe the multi-step molecular mechanism through which BoNTs enter nerve terminals and discuss the many levels at which the toxins can be inhibited. They review the outcomes of the different strategies adopted to limit neurotoxicity and counter intoxication. Potential new targets arising from the last discoveries of the mechanism of action and the approaches to promote neuromuscular junction recovery are also discussed. Expert opinion: Current drug discovery efforts have mainly focused on BoNT type A and addressed primarily light chain proteolytic activity. Development of pan-BoNT inhibitors acting independently of BoNT immunological properties and targeting a common step of the intoxication process should be encouraged.
Pharmacological Reviews, 2017
Toxins, Jan 18, 2017
Botulinum neurotoxins are diverse proteins. They are currently represented by at least seven sero... more Botulinum neurotoxins are diverse proteins. They are currently represented by at least seven serotypes and more than 40 subtypes. New clostridial strains that produce novel neurotoxin variants are being identified with increasing frequency, which presents challenges when organizing the nomenclature surrounding these neurotoxins. Worldwide, researchers are faced with the possibility that toxins having identical sequences may be given different designations or novel toxins having unique sequences may be given the same designations on publication. In order to minimize these problems, an ad hoc committee consisting of over 20 researchers in the field of botulinum neurotoxin research was convened to discuss the clarification of the issues involved in botulinum neurotoxin nomenclature. This publication presents a historical overview of the issues and provides guidelines for botulinum neurotoxin subtype nomenclature in the future.
Cellular Microbiology, 2016
Botulinum and tetanus neurotoxins are the most toxic substances known and form the growing family... more Botulinum and tetanus neurotoxins are the most toxic substances known and form the growing family of clostridial neurotoxins (CNTs). They are composed of a metalloprotease light chain (L), linked via a disulfide bond to a heavy chain (H). H mediates binding to nerve terminals and the membrane translocation of L into the cytosol where their substrates, the three SNARE proteins, are localized. L translocation is accompanied by unfolding and L has to be reduced and reacquire the native fold to exert its neurotoxicity. The Thioredoxin reductase-Thioredoxin system is responsible for the reduction, but it is unknown whether the refolding of L is spontaneous or aided by host chaperones. Here we report that geldanamycin, a specific inhibitor of Hsp90, hampers the refolding of L after membrane translocation and completely prevents the cleavage of SNAREs. We also found that the effect of geldanamycin strongly synergises with that of PX-12, an inhibitor of thioredoxin, suggesting that the processes of L chain refolding and interchain disulphide reduction are strictly coupled. Indeed we found that Hsp90 and the Thioredoxin reductase-Thioredoxin system physically interact on synaptic vesicle where they orchestrate a chaperone-redox machinery which is exploited by CNTs to deliver their catalytic part in the cytosol.
Molecular Microbiology, 1994
Tetanus and botulinum neurotoxins, produced by anaerobic bacteria of the genus Clostridium, are t... more Tetanus and botulinum neurotoxins, produced by anaerobic bacteria of the genus Clostridium, are the most toxic proteins known and are the sole responsible for the pathogenesis of tetanus and botulism. They enter peripheral cholinergic nerve terminals and cleave proteins of the neuroexocytosis apparatus causing a persistent, but reversible, inhibition of neurotransmitter release. Botulinum neurotoxins are used in the therapy of many human syndromes caused by hyperactive cholinergic nerve terminals. Here we focus on the many advances that were recently made on the understanding of their molecular mechanism of action and on their use in human therapy.
Journal of Anatomy
Schwann cells (SCs) are fundamental components of the peripheral nervous system (PNS) of all vert... more Schwann cells (SCs) are fundamental components of the peripheral nervous system (PNS) of all vertebrates and play essential roles in development, maintenance, function, and regeneration of peripheral nerves. There are distinct populations of SCs including: (1) myelinating SCs that ensheath axons by a specialized plasma membrane, called myelin, which enhances the conduction of electric impulses; (2) non-myelinating SCs, including Remak SCs, which wrap bundles of multiple axons of small caliber, and perysinaptic SCs (PSCs), associated with motor axon terminals at the neuromuscular junction (NMJ). All types of SCs contribute to PNS regeneration through striking morphological and functional changes in response to nerve injury, are affected in peripheral neuropathies and show abnormalities and a diminished plasticity during aging. Therefore, methodological approaches to study and manipulate SCs in physiological and pathophysiological conditions are crucial to expand the present knowledge on SC biology and to devise new therapeutic strategies to counteract neurodegenerative conditions and age-derived denervation. We present here an updated overview of traditional and emerging methodologies for the study of SCs for scientists approaching this research field.
Pharmaceuticals
Tetanus neurotoxin (TeNT) is a protein exotoxin produced by Clostridium tetani that causes the de... more Tetanus neurotoxin (TeNT) is a protein exotoxin produced by Clostridium tetani that causes the deadly spastic neuroparalysis of tetanus. It consists of a metalloprotease light chain and of a heavy chain linked via a disulphide bond. TeNT binds to the neuromuscular junction (NMJ) and it is retro-axonally transported into vesicular compartments to the spinal cord, where it is released and taken up by inhibitory interneuron. Therein, the catalytic subunit is translocated into the cytoplasm where it cleaves its target protein VAMP-1/2 with consequent blockage of the release of inhibitory neurotransmitters. Vaccination with formaldehyde inactivated TeNT prevents the disease, but tetanus is still present in countries where vaccination coverage is partial. Here, we show that small molecule inhibitors interfering with TeNT trafficking or with the reduction of the interchain disulphide bond block the activity of the toxin in neuronal cultures and attenuate tetanus symptoms in vivo. These fin...
Journal of Clinical Investigation
Human monoclonal antibodies were used here to study the mechanism of neuron intoxication by tetan... more Human monoclonal antibodies were used here to study the mechanism of neuron intoxication by tetanus neurotoxin and to evaluate them as a safe preventive and therapeutic substitute of hyperimmune sera for tetanus in mice. By screening memory B cells of immune donors, we selected two monoclonal antibodies specific for tetanus neurotoxin with exceptionally high neutralizing activities, which were extensively characterized both structurally and functionally. We found that these antibodies interfere with the binding and translocation of the neurotoxin into neurons by interacting with two epitopes, whose definition pinpoints crucial events in the cellular pathogenesis of tetanus. This information explains the unprecedented neutralization ability of these antibodies, which were found to be exceptionally potent in preventing experimental tetanus when injected in mice long before the neurotoxin. Moreover, their Fab derivatives neutralized tetanus neurotoxin in post-exposure experiments, suggesting their potential therapeutic use via intrathecal injection. As such, these human monoclonal antibodies, as well as their Fab derivatives, meet all requirements for being considered for prophylaxis and therapy of human tetanus and are ready for clinical trials.
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Papers by Marco Pirazzini