Determination of the Localization Patterns of the Alpha 1 and Alpha 2 Subunits of Actin Capping Protein

Actin is an abundant protein of eukaryotic cells that contributes to a variety of cellular processes including cell division, maintaining cell structure, mobility and muscle contraction. Monomeric actin can polymerize and depolymerize to form long filaments and branched structures. Actin dynamics are largely regulated by accessory proteins, including actin Capping Protein (CP). Capping Protein is a heterodimer composed of an alpha (α) and a beta (β) subunit. In higher organisms, there are three alpha isoforms (α1, α2, α3) and three beta isoforms (β1, β2, β3). In vertebrates, the α1 and α2 proteins are highly conserved, differing by approximately 20 amino acids. In previous Western Blot analysis using an antibody that recognizes α subunits equally, both α1 and α2 proteins accumulated in all mouse tissues examined; however, the relative amounts of the proteins varied among different tissues. The presence of multiple isoforms of the subunits of CP and their different expression levels in tissues raises the possibility of isoform specific functions. We have recently generated α1 and α2 polyclonal antibodies and confirmed their specificity. We are using the antibodies to define similarities and differences in the protein patterns of α isoforms using immunofluorescence studies. Both α1 and α2 had similar localization patterns in murine skeletal muscle, localizing to the Z-line. We are analyzing other tissues including spleen, liver, kidney, lung, and myocardium to determine if the α isoforms have distinct localization patterns