High impact information on Capg

• The coexistence of gCap39 with gelsolin should allow precise regulation of actin assembly at the leading edge of the cell [1].
• However, gCap39 does not sever actin filaments and can respond to Ca2+ and PPI transients independently, under conditions in which gelsolin is ineffective [1].
• Examination of Mbh1 localization in 3T3 fibroblasts by indirect immunofluorescence reveals a larger cell population showing diffuse staining, and a smaller population exhibiting a distinct nuclear stain [2].
• Embedded within the amino acid sequence encoded by mbh1 is a region distantly related to the basic/helix-loop-helix (B/HLH) DNA-binding motif and a potential nuclear localization signal [2].
• Translation of mbh1 RNA in rabbit reticulocyte extracts produces an approximately 45 kd protein capable of binding actin-coupled agarose beads in vitro in a Ca2(+)-dependent manner [2].

Biological context of Capg

• Western analysis corroborates this intracellular localization and indicates that total cellular levels and localization of Mbh1 are not affected by the cell growth state [2].
• The phosphorylation state of gCap39 in cells is therefore regulated by a balance between kinases and okadaic acid-sensitive phosphatases, and phosphorylation sites containing threonines appear to be particularly sensitive to the phosphatases [3].
• Nuclear gCap39 redistributes throughout the cytoplasm during mitosis and is excluded from regions containing chromosomes [4].

Anatomical context of Capg

• Purification and expression of gCap39. An intracellular and secreted Ca2(+)-dependent actin-binding protein enriched in mononuclear phagocytes [5].
• When an expression vector containing the gCap39 coding region was transfected into COS cells, high levels of gCap39 were found in both the cells and conditioned media, whereas annexins were only present in the cells. gCap39 could also be purified from human plasma where it appeared to be a minor component [5].
• We found that gCap39 is very abundant in macrophages (accounting for 0.6% of total macrophage proteins), and is present in 12-fold molar excess to gelsolin [4].
• Both proteins are highly induced during differentiation of the promyelocytic leukemia cell line into macrophages. gCap39 is less abundant in fibroblasts (0.04% total proteins) and is present in equal molar ratio to gelsolin [4].

Other interactions of Capg

• Mbh1 encodes a polypeptide structurally similar to the actin-severing proteins gelsolin and severin [2].
• We describe the characterization of a novel cDNA, mbh1 (myc basic motif homolog-1), which was found during a search for candidate factors which might interact with the c-Myc oncoprotein [2].
• A number of macrophage proteins, i.e., gal-3, Capg, and MCP-4, were expressed at increased levels and immunohistochemical analyses revealed an increased infiltration of F4/80+ cells [6].
• Okadaic acid, a protein phosphatase inhibitor, stimulates gCap39 phosphorylation in vivo [3].
• We conclude that phospho-gCap39 is preferentially associated with nuclei and suggest that phosphorylation of gCap39 is functionally significant [3].

References