title: Interaction of microtubule-associated protein-2 and p63: a new link between microtubules and rough endoplasmic reticulum membranes in neurons.
abstract: Neurons are polarized cells presenting two distinct compartments, dendrites and an axon. Dendrites can be distinguished from the axon by the presence of rough endoplasmic reticulum (RER). The mechanism by which the structure and distribution of the RER is maintained in these cells is poorly understood. In the present study, we investigated the role of the dendritic microtubule-associated protein-2 (MAP2) in the RER membrane positioning by comparing their distribution in brain subcellular fractions and in primary hippocampal cells and by examining the MAP2-microtubule interaction with RER membranes in vitro. Subcellular fractionation of rat brain revealed a high MAP2 content in a subfraction enriched with the endoplasmic reticulum markers ribophorin and p63. Electron microscope morphometry confirmed the enrichment of this subfraction with RER membranes. In cultured hippocampal neurons, MAP2 and p63 were found to concomitantly compartmentalize to the dendritic processes during neuronal differentiation. Protein blot overlays using purified MAP2c protein revealed its interaction with p63, and immunoprecipitation experiments performed in HeLa cells showed that this interaction involves the projection domain of MAP2. In an in vitro reconstitution assay, MAP2-containing microtubules were observed to bind to RER membranes in contrast to microtubules containing tau, the axonal MAP. This binding of MAP2c microtubules was reduced when an anti-p63 antibody was added to the assay. The present results suggest that MAP2 is involved in the association of RER membranes with microtubules and thereby could participate in the differential distribution of RER membranes within a neuron.
authors.affiliation: Département de Pathologie et Biologie Cellulaire, Université de Montréal, CP 6128, Succ. Centre-ville, Montréal, Québec H3C 3J7, Canada.
authors.forename: Carole Abi
authors.initials: CA
authors.lastname: Farah
authors.forename: Dalinda
authors.initials: D
authors.lastname: Liazoghli
authors.forename: Sébastien
authors.initials: S
authors.lastname: Perreault
authors.forename: Mylène
authors.initials: M
authors.lastname: Desjardins
authors.forename: Alain
authors.initials: A
authors.lastname: Guimont
authors.forename: Angela
authors.initials: A
authors.lastname: Anton
authors.forename: Michel
authors.initials: M
authors.lastname: Lauzon
authors.forename: Gert
authors.initials: G
authors.lastname: Kreibich
authors.forename: Jacques
authors.initials: J
authors.lastname: Paiement
authors.forename: Nicole
authors.initials: N
authors.lastname: Leclerc
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D004622:Embryo, Mammalian; D004625:Embryo, Nonmammalian; D004721:Endoplasmic Reticulum / Q000502:physiology / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D006624:Hippocampus / Q000502:physiology; D007425:Intracellular Membranes / Q000378:metabolism; D008854:Microscopy, Electron; D008861:Microsomes / Q000378:metabolism / Q000648:ultrastructure; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D009474:Neurons / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D018411:Spodoptera; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
chemical_list: C489787:MAP2 protein, rat; D008869:Microtubule-Associated Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors