title: The stress-regulated protein M6a is a key modulator for neurite outgrowth and filopodium/spine formation.
abstract: Neuronal remodeling is a fundamental process by which the brain responds to environmental influences, e.g., during stress. In the hippocampus, chronic stress causes retraction of dendrites in CA3 pyramidal neurons. We have recently identified the glycoprotein M6a as a stress-responsive gene in the hippocampal formation. This gene is down-regulated in the hippocampus of both socially and physically stressed animals, and this effect can be reversed by antidepressant treatment. In the present work, we analyzed the biological function of the M6a protein. Immunohistochemistry showed that the M6a protein is abundant in all hippocampal subregions, and subcellular analysis in primary hippocampal neurons revealed its presence in membrane protrusions (filopodia/spines). Transfection experiments revealed that M6a overexpression induces neurite formation and increases filopodia density in hippocampal neurons. M6a knockdown with small interference RNA methodology showed that M6a low-expressing neurons display decreased filopodia number and a lower density of synaptophysin clusters. Taken together, our findings indicate that M6a plays an important role in neurite/filopodium outgrowth and synapse formation. Therefore, reduced M6a expression might be responsible for the morphological alterations found in the hippocampus of chronically stressed animals. Potential mechanisms that might explain the biological effects of M6a are discussed.
authors.affiliation: Instituto de Investigaciones Biotecnológicas-INTECH Universidad Nacional Gral. San Martín y Consejo Nacional de Investigaciones Científicas y Técnicas, 1650 San Martín, Argentina. julialfo@iib.unsam.edu.ar
authors.forename: Julieta
authors.initials: J
authors.lastname: Alfonso
authors.forename: María E
authors.initials: ME
authors.lastname: Fernández
authors.forename: Benjamin
authors.initials: B
authors.lastname: Cooper
authors.forename: Gabriele
authors.initials: G
authors.lastname: Flugge
authors.forename: Alberto C
authors.initials: AC
authors.lastname: Frasch
mesh_terms: D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000235:genetics / Q000473:pathology / Q000502:physiology; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D049229:Dendritic Spines / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology* / Q000502:physiology / Q000503:physiopathology; D008297:Male; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D016501:Neurites / Q000502:physiology*; D009473:Neuronal Plasticity / Q000235:genetics; D009474:Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D016716:PC12 Cells; D011554:Pseudopodia / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D013312:Stress, Physiological / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D014162:Transfection
chemical_list: C484159:Gpm6a protein, rat; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering