Potentiation of receptor responses induced by prolonged binding of Gα13 and leukemia-associated RhoGEF

Diverse cellular functions are controlled by RhoA-GTPases, which are activated by trimeric G proteins via RhoGEFs, among others. In this study, we focused on the signaling from GPCRs to RhoA via G alpha(13) and leukemia-associated RhoGEF (LARG). The activation of G alpha(13) was elucidated in living cells with high temporal and spatial resolution by means of FRET. The inactivation after agonist withdrawal occurred in the same range (t(1/2)=25.3 +/- 2.2 s; mean +/- SEM; n=22) as described for other G alpha proteins. The interaction of G alpha(13) and LARG and the thereby-induced LARG translocation to the plasma membrane were at least 1 order of magnitude more stable after agonist withdrawal, exceeding G alpha(13) deactivation in the absence of LARG several fold. Consequently, we observed an almost 100-fold higher agonist sensitivity of the G alpha(13) LARG interaction compared to the G alpha(13) activation in the absence of LARG.