title: Parkin binds to alpha/beta tubulin and increases their ubiquitination and degradation.
abstract: In addition to inhibiting the mitochondrial respiratory chain, toxins known to cause Parkinson's disease (PD), such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and rotenone, also strongly depolymerize microtubules and increase tubulin degradation. Microtubules are polymers of tubulin alpha/beta heterodimers, whose correct folding requires coordinated actions of cellular chaperonins and cofactors. Misfolded tubulin monomers are highly toxic and quickly degraded through a hitherto unknown mechanism. Here we report that parkin, a protein-ubiquitin E3 ligase linked to PD, was tightly bound to microtubules in taxol-mediated microtubule coassembly assays. In lysates from the rat brain or transfected human embryonic kidney (HEK) 293 cells, alpha-tubulin and beta-tubulin were strongly coimmunoprecipitated with parkin at 4 degrees C in the presence of colchicine, a condition in which tubulin exits as alpha/beta heterodimers. At the subcellular level, parkin exhibited punctate immunostaining along microtubules in rat brain sections, cultured primary neurons, glial cells, and cell lines. This pattern of subcellular localization was abolished in cells treated with the microtubule-depolymerizing drug colchicine. The binding between parkin and tubulin apparently led to increased ubiquitination and accelerated degradation of alpha- and beta-tubulins in HEK293 cells. Similarly ubiquitinated tubulins were also observed in rat brain lysates. Furthermore, parkin mutants found in PD patients did not ubiquitinate or degrade either tubulin. Taken together, our results show that parkin is a novel tubulin-binding protein, as well as a microtubule-associated protein. Its ability to enhance the ubiquitination and degradation of misfolded tubulins may play a significant role in protecting neurons from toxins that cause PD.
authors.affiliation: Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Ren
authors.forename: Jinghui
authors.initials: J
authors.lastname: Zhao
authors.forename: Jian
authors.initials: J
authors.lastname: Feng
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D002478:Cells, Cultured; D003078:Colchicine / Q000494:pharmacology; D019281:Dimerization; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008025:Ligases / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D014404:Tubulin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism*
chemical_list: C093429:MAP1A protein, human; C490547:MAP1A protein, mouse; C490546:Map1a protein, rat; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D014404:Tubulin; D014452:Ubiquitins; C033652:postsynaptic density proteins; D044767:Ubiquitin-Protein Ligases; C111567:parkin protein; D008025:Ligases; D017239:Paclitaxel; D003078:Colchicine