title: Src-dependent aprotein kinase C iota/lambda (aPKCiota/lambda) tyrosine phosphorylation is required for aPKCiota/lambda association with Rab2 and glyceraldehyde-3-phosphate dehydrogenase on pre-golgi intermediates.
abstract: The small GTPase Rab2 is required for membrane transport between the endoplasmic reticulum (ER) and the Golgi complex. Rab2 associates with pre-Golgi intermediates (also termed vesicular tubular clusters; VTCs) that sort cargo to the anterograde pathway from recycling proteins retrieved to the ER. Our previous studies have shown that Rab2 stimulates atypical protein kinase C iota/lambda (aPKCiota/lambda) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) recruitment to VTCs. Both aPKCiota/lambda and GAPDH bind directly to Rab2 and aPKCiota/lambda and GAPDH interact. Based on the reports demonstrating aPKCiota-Src interaction and Src activity in the retrograde pathway (Golgi-ER), studies were initiated to learn whether Rab2 also promoted Src recruitment to VTCs. Using a quantitative membrane binding assay, we found that Rab2-stimulated Src membrane association in a dose-dependent manner. The recruited Src binds to aPKCiota/lambda and GAPDH on the membrane; however, Src does not interact with Rab2. The membrane-associated Src tyrosine phosphorylates aPKCiota/lambda on the VTC. To determine the consequence of aPKCiota/lambda tyrosine phosphorylation, the membrane binding assay was supplemented with the Src-specific tyrosine kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo(3,4-d)pyrimidine (PP2). Although Rab2, Src, and GAPDH recruitment was not affected, the Rab2-PP2-treated membranes contained a negligible amount of aPKCiota/lambda. Since Rab2 requires aPKCiota/lambda for the downstream recruitment of beta-coat protein (beta-COP) to VTCs, the Rab2-PP2-treated membranes were evaluated for the presence of beta-COP. Like aPKCiota/lambda, the membranes contained a negligible amount of beta-COP that was reflected by the drastic reduction in Rab2-dependent vesicle formation. These data suggest that Src-mediated tyrosine phosphorylation of aPKCiota/lambda facilitates aPKCiota/lambda association with Rab2-Src-GAPDH on VTCs, which is ultimately necessary for the downstream recruitment of beta-COP and release of Rab2-mediated retrograde-directed vesicles.
authors.affiliation: Department of Pharmacology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
authors.forename: Ellen J
authors.initials: EJ
authors.lastname: Tisdale
authors.forename: Cristina R
authors.initials: CR
authors.lastname: Artalejo
mesh_terms: D000818:Animals; D002460:Cell Line; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral; D020756:Coatomer Protein / Q000032:analysis / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D006639:Histidine / Q000737:chemistry; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000166:cytology; D008163:Luminescent Measurements; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D020693:rab2 GTP-Binding Protein / Q000378:metabolism*; D019061:src-Family Kinases / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism; D000099293:Protein Kinase C-lambda
chemical_list: D020756:Coatomer Protein; D004791:Enzyme Inhibitors; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D006639:Histidine; D007527:Isoenzymes; D011493:Protein Kinase C; D011743:Pyrimidines; D011994:Recombinant Proteins; D014443:Tyrosine; D020693:rab2 GTP-Binding Protein; D019061:src-Family Kinases; D000099293:Protein Kinase C-lambda; C412373:AG 1879