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Rho‐mediated cytoskeletal rearrangement in response to LPA is functionally antagonized by Rac1 and PIP 2
Author(s) -
Seasholtz Tammy M.,
RadeffHuang Julie,
Sagi Sarah A.,
Matteo Rosalia,
Weems Jessica M.,
Cohen Annemarie Stoudt,
Feramisco James R.,
Brown Joan Heller
Publication year - 2004
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2004.02749.x
Subject(s) - rhoa , lysophosphatidic acid , rac1 , microbiology and biotechnology , pertussis toxin , thrombin , receptor , biology , cytoskeleton , thrombin receptor , signal transduction , g protein , cell , biochemistry , immunology , platelet
G‐protein‐coupled receptors signal through Rho to induce actin cytoskeletal rearrangement. We previously demonstrated that thrombin stimulates Rho‐dependent process retraction and rounding of 1321N1 astrocytoma cells. Surprisingly, while lysophosphatidic acid (LPA) activated RhoA in 1321N1 cells, it failed to produce cell rounding. Thrombin, unlike LPA, decreased Rac1 activity, and activated (GTPase‐deficient) Rac1 inhibited thrombin‐stimulated cell rounding, while expression of dominant‐negative Rac1 promoted LPA‐induced rounding. LPA and thrombin receptors appear to differ in coupling to G i , as LPA but not thrombin‐stimulated 1321N1 cell proliferation was pertussis toxin‐sensitive. Blocking G i with pertussis toxin enabled LPA to induce cell rounding and to decrease activated Rac1. These data support the hypothesis that Rac1 and G i activation antagonize cell rounding. Thrombin and LPA receptors also differentially activated G q pathways as thrombin but not LPA increased InsP 3 formation and reduced phosphatidylinositol 4,5‐bisphosphate (PIP 2 ) levels. Microinjection of the plekstrin homology domain of phospholipase C (PLC)δ 1 , which binds PIP 2 , enabled LPA to elicit cell rounding, consistent with a requirement for PIP 2 reduction. We suggest that Rho‐mediated cytoskeletal responses are enhanced by concomitant reductions in cellular levels of PIP 2 and Rac1 activation and thus effected only by G‐protein‐coupled receptors with appropriate subsets of G protein activation.