title: Colocalisation of the protein tyrosine phosphatases PTP-SL and PTPBR7 with beta4-adaptin in neuronal cells.
abstract: The mouse gene Ptprr encodes the neuronal protein tyrosine phosphatases PTP-SL and PTPBR7. These proteins differ in their N-terminal domains, with PTP-SL being a cytosolic, membrane-associated phosphatase and PTPBR7 a type I transmembrane protein. In this study, we further explored the nature of the PTP-SL-associated vesicles in neuronal cells using a panel of organelle markers and noted a comparable subcellular distribution for PTP-SL and the beta4-adaptin subunit of the AP4 complex. PTP-SL, PTPBR7 and beta4-adaptin are localised at the Golgi apparatus and at vesicles throughout the cytoplasm. Immunohistochemical analysis demonstrated that PTP-SL, PTPBR7 and beta4-adaptin are all endogenously expressed in brain. Interestingly, coexpression of PTP-SL and beta4-adaptin leads to an altered subcellular localisation for PTP-SL. Instead of the Golgi and vesicle-type staining pattern, still observable for beta4-adaptin, PTP-SL is now distributed throughout the cytoplasm. Although beta4-adaptin was found to interact with the phosphatase domain of PTP-SL and PTPBR7 in the yeast two-hybrid system, it failed to do so in transfected neuronal cells. Our data suggest that the tyrosine phosphatases PTP-SL and PTPBR7 may be involved in the formation and transport of AP4-coated vesicles or in the dephosphorylation of their transmembrane cargo molecules at or near the Golgi apparatus.
authors.affiliation: Department of Cell Biology, Nijmegen Center for Molecular Life Sciences, University Medical Center St. Radboud, Geert Grooteplein Zuid 28, 6525 GA Nijmegen, The Netherlands.
authors.forename: Gönül
authors.initials: G
authors.lastname: Dilaver
authors.forename: Jan
authors.initials: J
authors.lastname: Schepens
authors.forename: Arn
authors.initials: A
authors.lastname: van den Maagdenberg
authors.forename: Mietske
authors.initials: M
authors.lastname: Wijers
authors.forename: Barry
authors.initials: B
authors.lastname: Pepers
authors.forename: Jack
authors.initials: J
authors.lastname: Fransen
authors.forename: Wiljan
authors.initials: W
authors.lastname: Hendriks
mesh_terms: D033966:Adaptor Protein Complex beta Subunits / Q000378:metabolism*; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D001921:Brain / Q000201:enzymology; D019556:COS Cells; D002522:Chlorocebus aethiops; D006056:Golgi Apparatus / Q000201:enzymology / Q000648:ultrastructure; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000201:enzymology* / Q000648:ultrastructure; D016716:PC12 Cells / Q000201:enzymology* / Q000648:ultrastructure; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D051381:Rats; D054634:Receptor-Like Protein Tyrosine Phosphatases, Class 7; D014162:Transfection; D022161:Transport Vesicles / Q000201:enzymology / Q000648:ultrastructure
chemical_list: D033966:Adaptor Protein Complex beta Subunits; D015415:Biomarkers; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; C513469:PTPRR protein, human; D017027:Protein Tyrosine Phosphatases; C513472:Ptprr protein, mouse; C513471:Ptprr protein, rat; D054634:Receptor-Like Protein Tyrosine Phosphatases, Class 7