Lysophosphatidic Acid and Thrombin Receptors Require Both Gα₁₂ and Gα₁₃ to Regulate Axonal Morphology in Hippocampal Neurons

Abstract

The Gα subunits of the G₁₂ family of heterotrimeric guanine nucleotide-binding proteins (G proteins), defined by Gα₁₂ and Gα₁₃, have many cellular functions in common, including stimulation of stress fiber formation and focal adhesion assembly via the small GTPase RhoA activation. We and others previously showed that Gα₁₂ and Gα₁₃ mediate neurite retraction in neuronal cell lines, but their roles in primary cultured neurons have not been adequately understood. Here, we found that expression of constitutively active mutants of Gα₁₂ or Gα₁₃ caused growth cone collapse dependent on Rho-kinase activity in hippocampal neurons. The stimulation of thrombin and lysophosphatidic acid (LPA) receptors, which have been thought to selectively couple to Gα₁₂ and Gα₁₃, respectively, caused growth cone collapse and suppressed axon branching dependent on Rho-kinase activity in hippocampal neurons. Thrombin- and LPA-induced growth cone collapse was suppressed by both single knockdown of Gα₁₂ and Gα₁₃ with short hairpin RNAs and this suppression was augmented by double knockdown of both Gα₁₂ and Gα₁₃. These results suggest that thrombin and LPA receptors couple to both Gα₁₂ and Gα₁₃ for growth cone collapse.