Identification of a novel, putative Rho-specific GDP/GTP exchange factor and a RhoA-binding protein: control of neuronal morphology

MFBG Gebbink, O Kranenburg, M Poland… - The Journal of cell …, 1997 - rupress.org
MFBG Gebbink, O Kranenburg, M Poland, FPG Horck, B Houssa, WH Moolenaar
The Journal of cell biology, 1997rupress.org
The small GTP-binding protein Rho has been implicated in the control of neuronal
morphology. In N1E-115 neuronal cells, the Rho-inactivating C3 toxin stimulates neurite
outgrowth and prevents actomyosin-based neurite retraction and cell rounding induced by
lysophosphatidic acid (LPA), sphingosine-1-phosphate, or thrombin acting on their cognate
G protein–coupled receptors. We have identified a novel putative GDP/GTP exchange factor,
RhoGEF (190 kD), that interacts with both wild-type and activated RhoA, but not with Rac or …
The small GTP-binding protein Rho has been implicated in the control of neuronal morphology. In N1E-115 neuronal cells, the Rho-inactivating C3 toxin stimulates neurite outgrowth and prevents actomyosin-based neurite retraction and cell rounding induced by lysophosphatidic acid (LPA), sphingosine-1-phosphate, or thrombin acting on their cognate G protein–coupled receptors. We have identified a novel putative GDP/GTP exchange factor, RhoGEF (190 kD), that interacts with both wild-type and activated RhoA, but not with Rac or Cdc42. RhoGEF, like activated RhoA, mimics receptor stimulation in inducing cell rounding and in preventing neurite outgrowth. Furthermore, we have identified a 116-kD protein, p116Rip, that interacts with both the GDP- and GTP-bound forms of RhoA in N1E-115 cells. Overexpression of p116Rip stimulates cell flattening and neurite outgrowth in a similar way to dominant-negative RhoA and C3 toxin. Cells overexpressing p116Rip fail to change their shape in response to LPA, as is observed after Rho inactivation. Our results indicate that (a) RhoGEF may link G protein–coupled receptors to RhoA activation and ensuing neurite retraction and cell rounding; and (b) p116Rip inhibits RhoA-stimulated contractility and promotes neurite outgrowth.
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