Activation of the GTPase Cdc42 leads to a different set of actin rearrangements from those brought about by activation of the GTPase Rho. It is known that Arp2/3 proteins are targets of Cdc42, whereas Formins are targets of Rho1. Both Arp2/3 and Formins promote actin polymerization. Explain why the activation of these two GTPases could lead to differences in the actin cytoskeleton.

Arp2/3 and formins differ in their mechanisms of actin polymerization

Explanation:

The actin cytoskeleton plays key roles in diverse cellular processes including, among others, morphogenesis and endocytosis. The Arp2/3 complex and formin family proteins are two different types of actin-binding proteins capable of modulating the dynamics of actin filaments. The Arp2/3 complex is well known to have a key role in spine morphogenesis by promoting the branching of existing actin filaments. On the other hand, formin proteins induce the formation of plasma membrane protrusions by promoting the formation of unbranched filaments.