Contribution Of Residue 188 Identity To Rhoa And Rhoc Membrane Association

Presence of a negative charge at RhoA residue 188, such as through PKA‐catalyzed serine phosphorylation, has been found to destabilize RhoA membrane association. Closely related RhoC retains an adjacent canonical PKA recognition sequence (KRR), but possesses an Arg residue in place of serine at position 188. Therefore, we propose divergence at residue 188 between these two Rho isoforms directly impacts membrane association. We found transiently expressed RhoC more membrane associated than RhoA when expressed in ovarian cancer cells. Using a residue swap approach, RhoA‐S188R was found more membrane associated than wild‐type RhoA, while RhoC‐R188S had similar membrane association as wild‐type RhoC. At the same time, RhoC‐R188S was more effectively driven from membranes following forskolin treatment than RhoC. Altogether, these data suggest that a positively charged residue at position 188 strengthens RhoC membrane association and provides a mechanism for regulatory divergence.