The C1 domain of Vav3, a novel potential therapeutic target

Abstract

Vav1/2/3 comprise a protein family with guanyl nucleotide exchange activity for Rho and Rac as well as with motifs conferring adapter activity. Biologically, Vav1 plays a critical role in hematologic cell signaling, whereas Vav2/3 have a wider tissue distribution, but all 3 Vav proteins are implicated in cancer development. A structural feature of Vav1/2/3 is the presence of an atypical C1 domain, which possesses close structural homology to the typical C1 domains of protein kinase C but which fails to bind the second messenger diacylglycerol or the potent analogs, the phorbol esters. Previously, we have shown that five residues in the Vav1 C1 domain are responsible for its lack of phorbol ester binding. Here, we show that the lack of phorbol ester binding of Vav3 has a similar basis. We then explore the consequences of phorbol ester binding to a modified Vav3 in which the C1 domain has been altered to allow phorbol ester binding. We find both disruption of the guanyl nucleotide exchange activity of the modified Vav 3 as well as a shift in localization to the membrane upon phorbol ester treatment. This change in localization is associated with altered interactions with other signaling proteins. The studies provide a first step in assessing the potential for the design of custom C1 domain targeted molecules selective for the atypical C1 domains of Vav family proteins.

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“…Vav proteins are composed of different structural motifs: a Dbl homology (DH) domain, a calponin homology (CH) domain, a C-terminal pleckstrin homology (PH) domain, and a C1 domain. Recently, the C1 domain of Vav proteins and of Vav3 in particular, has been identified as a potential therapeutic target to inhibit the members of this family [154,155]. This Vav fragment is an atypical C1 domain with close homology to the one of protein kinase C. But in contrast to the latter, the C1 motif of Vavs is not able to bind phorbol esters [154].…”

“…This specificity has been used to disrupt the signaling cascade downstream of Vav3 by expressing a modified Vav3 with a C1 domain able to bind phorbol ester that in turn acts as a dominant-negative form. Expression of a variant of Vav3 with this modified C1 domain leads to a change of the Vav3 localization, now found at the plasma membrane instead of the cytoplasm, leading to a disruption of the interactions with its partners [155].…”