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J Biol Chem. 2014 Jun 20;289(25):17689-98. doi: 10.1074/jbc.M113.536227. Epub 2014 May 1.

The Ras-related protein, Rap1A, mediates thrombin-stimulated, integrin-dependent glioblastoma cell proliferation and tumor growth.

Author information

1
From the Departments of Pharmacology and.
2
Pathology, University of California at San Diego, La Jolla, California 92093 and.
3
the Department of Biochemistry and Molecular Biology, Indiana University, Indianapolis, Indiana 46202.
4
From the Departments of Pharmacology and jhbrown@ucsd.edu.

Abstract

Rap1 is a Ras family GTPase with a well documented role in ERK/MAP kinase signaling and integrin activation. Stimulation of the G-protein-coupled receptor PAR-1 with thrombin in human 1321N1 glioblastoma cells led to a robust increase in Rap1 activation. This response was sustained for up to 6 h and mediated through RhoA and phospholipase D (PLD). Thrombin treatment also induced a 5-fold increase in cell adhesion to fibronectin, which was blocked by down-regulating PLD or Rap1A or by treatment with a β1 integrin neutralizing antibody. In addition, thrombin treatment led to increases in phospho-focal adhesion kinase (tyrosine 397), ERK1/2 phosphorylation and cell proliferation, which were significantly inhibited in cells treated with β1 integrin antibody or Rap1A siRNA. To assess the role of Rap1A in tumor formation in vivo, we compared growth of 1321N1 cells stably expressing control, Rap1A or Rap1B shRNA in a mouse xenograft model. Deletion of Rap1A, but not of Rap1B, reduced tumor mass by >70% relative to control. Similar observations were made with U373MG glioblastoma cells in which Rap1A was down-regulated. Collectively, these findings implicate a Rap1A/β1 integrin pathway, activated downstream of G-protein-coupled receptor stimulation and RhoA, in glioblastoma cell proliferation. Moreover, our data demonstrate a critical role for Rap1A in glioblastoma tumor growth in vivo.

KEYWORDS:

Cell Proliferation; Cell Signaling; G-protein-coupled Receptor (GPCR); Glioblastoma; Integrin; Rap1; Small GTPase; Thrombin

PMID:
24790104
PMCID:
PMC4067203
DOI:
10.1074/jbc.M113.536227
[Indexed for MEDLINE]
Free PMC Article

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