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Integrin α3β1 interacts with I1PP2A/lanp and phosphatase PP1

✍ Scribed by Diana Mutz; Christoph Weise; Nadja Mechai; Werner Hofmann; Rüdiger Horstkorte; Gerold Brüning; Kerstin Danker

Publisher
John Wiley and Sons
Year
2006
Tongue
English
Weight
456 KB
Volume
84
Category
Article
ISSN
0360-4012

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✦ Synopsis

Abstract

Integrin α3β1 is a receptor for the extracellular matrix component laminin 5. To elucidate possible signaling pathways induced by integrin α3β1, we looked for proteins that interact with the cytoplasmic part of the α3A 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 α3A 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 α3A/cyto‐binding protein. PP1 and integrin α3β1 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 α integrin subunit, whereas I1PP2A/lanp requires a longer sequence for binding. PP1 but not PP2A is able to dephosphorylate precipitated integrin α3β1 in vitro. Furthermore, PP1 releases phosphate from T1046 of phosphopeptides that mimic the phosphorylation consensus sequence in the cytoplasmic part of the α3A integrin subunit. These data suggest that I1PP2A/lanp forms a complex with PP1 and the α3A integrin subunit and might possibly regulate the phosphorylation status of integrin α3β1 and/or integrin downstream targets. © 2006 Wiley‐Liss, Inc.

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