MDia3 (Ser-196) ) [conserved site], Phosphospecific Antibody

Formins include several families of proteins that regulate actin cytoskeletal dynamics via two conserved formin homology domains, FH1 and FH2. Through cooperation of FH1 and FH2, formins construct actin-based structures comprising linear, unbranched filaments that are used in stress fibers, actin cables, microspikes, and contractile rings. A subgroup of the formins is the diaphanous (Dia) family, which includes mDia1 (Diap1), mDia2 (Diap3), and mDia3 (Diap2) . mDia3 is activated by Cdc42 and regulates the attachment of microtubules to the kinetochore during mitosis. Aurora B kinase phosphorylates Ser-196 and Thr-882 in vitro, and phosphorylation of Ser-196 increases during mitosis in vivo. A multisite mutant mDia3 with nonphosphorylatable T66A, S196A, S880A and T882A leads to misalignment of chromosomes at the metaphase plate. Thus, phosphorylation may be an important regulator of mDia3 activity during mitosis.

The antibody detects a 130 kDa* protein corresponding to the apparent molecular mass of mDia3 on SDS-PAGE immunoblots of human Jurkat treated with calyculin A. This reactivity is not observed after lambda phosphatase treatment. The antibody may also detect phosphorylated mDia1/Diap1 (Ser-171) and mDia2/Diap3 (Ser-202) . This peptide sequence is identical in rat and mouse mDia3, and the site is well conserved in human mDia1/Diap1 (Ser-171) and mDia2/Diap3 (Ser-202) .