title: Integrin alpha3beta1 interacts with I1PP2A/lanp and phosphatase PP1.
abstract: Integrin alpha3beta1 is a receptor for the extracellular matrix component laminin 5. To elucidate possible signaling pathways induced by integrin alpha3beta1, we looked for proteins that interact with the cytoplasmic part of the alpha3A integrin subunit. We identified several multifunctional proteins by affinity chromatography and subsequent MALDI-TOF-MS and focused on the inhibitor 1 of serine/threonine phosphatase PP2A (I1PP2A, synonym: lanp) which also plays a role during the development of the mouse cerebellum. I1PP2A/lanp colocalizes with the alpha3A integrin subunit in differentiated PC12 cells in the cell body and in neurites as well as in Purkinje cells of mouse cerebellum. Overexpression of GFP-I1PP2A/lanp in PC12 cells leads to markedly reduced neurite length on laminin 5 after induction with nerve growth factor. By affinity chromatography the protein phosphatase PP1 can also be identified as a alpha3A/cyto-binding protein. PP1 and integrin alpha3beta1 can be pulled down by GST-I1PP2A/lanp from cell lysates of differentiated and undifferentiated PC12 cells. The phosphatase binds to the cytoplasmic membrane-proximal conserved GFFKR motif of the alpha integrin subunit, whereas I1PP2A/lanp requires a longer sequence for binding. PP1 but not PP2A is able to dephosphorylate precipitated integrin alpha3beta1 in vitro. Furthermore, PP1 releases phosphate from T1046 of phosphopeptides that mimic the phosphorylation consensus sequence in the cytoplasmic part of the alpha3A integrin subunit. These data suggest that I1PP2A/lanp forms a complex with PP1 and the alpha3A integrin subunit and might possibly regulate the phosphorylation status of integrin alpha3beta1 and/or integrin downstream targets.
authors.affiliation: Institut für Molekularbiologie und Biochemie, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin-Dahlem, Germany.
authors.forename: Diana
authors.initials: D
authors.lastname: Mutz
authors.forename: Christoph
authors.initials: C
authors.lastname: Weise
authors.forename: Nadja
authors.initials: N
authors.lastname: Mechai
authors.forename: Werner
authors.initials: W
authors.lastname: Hofmann
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Horstkorte
authors.forename: Gerold
authors.initials: G
authors.lastname: Brüning
authors.forename: Kerstin
authors.initials: K
authors.lastname: Danker
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D015153:Blotting, Western / Q000379:methods; D064026:Calbindins; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002846:Chromatography, Affinity / Q000379:methods; D015870:Gene Expression / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D039201:Integrin alpha3beta1 / Q000378:metabolism*; D016501:Neurites / Q000502:physiology; D016716:PC12 Cells; D010446:Peptide Fragments / Q000378:metabolism; D010449:Peptide Mapping / Q000379:methods; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011485:Protein Binding / Q000502:physiology; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D014162:Transfection
chemical_list: D064026:Calbindins; D039201:Integrin alpha3beta1; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D064030:S100 Calcium Binding Protein G; C054547:atrial natriuretic factor prohormone (1-30), human; D049452:Green Fluorescent Proteins; D011189:Potassium Chloride; D009320:Atrial Natriuretic Factor; C089504:polyphosphoinositide phosphatase; D010744:Phosphoric Monoester Hydrolases