cDNA cloning and characterization of macrophage capping protein

Guissou Alavi Dabiri, University of Pennsylvania


Macrophage Capping Protein (MCP) is a Ca$\sp{2+}$-sensitive protein, originally purified from rabbit alveolar macrophages, which reversibly blocks the barbed ends of actin filaments (Southwick, F. S. & DiNubile, M. J. 1986. J. Biol. Chem. 261:14191-14195). In contrast to all the other Ca$\sp{2+}$-sensitive barbed-end blocking proteins, MCP does not sever preformed actin filaments. In this study, we report the isolation of the human cDNA for MCP from a $\lambda$gt10 U937 library. Sequence comparison with other actin binding proteins indicates that MCP is a member of the gelsolin/villin and fragmin/severin family of barbed-end blocking and severing proteins. Like the severing proteins, MCP is organized into repeating domains, $\approx$14 kDa in size. Two sequences in the first domain of MCP diverge markedly from those in the severing proteins. These regions may have an important role in actin filament severing in the other proteins. Sequence analysis also revealed that MCP is the human homologue of the mouse gCap39 and Mbh1, which have been independently cloned by other investigators. Tissue distribution data by Northern and Western analysis suggest that MCP is predominantly found in macrophages and monocytes. In addition, during PMA-induced differentiation of myeloid cell lines U937 and HL60 into macrophage-like cells there is a 3-fold and a 8-fold increase, respectively, in the mRNA levels for MCP while the levels for actin remain essentially unchanged. The pattern of expression for gelsolin mRNA, however, is different in developing macrophages. A 4-fold increase in MCP mRNA levels was also observed in granulocyte differentiation of DMSO-treated HL60 cells. Southern blots suggest that the MCP gene is present in a single copy in the human genome and most likely resides on chromosome 2.

Subject Area

Cellular biology|Molecular biology

Recommended Citation

Dabiri, Guissou Alavi, "cDNA cloning and characterization of macrophage capping protein" (1992). Dissertations available from ProQuest. AAI9227646.