Mammary gland Ca2+-binding (-dependent) proteins: Identification as calelectrins and calpactin I/p36

✍ Scribed by Yun Kit Hom; Thomas C. Sudhof; Joseph J. Lozano; Alfred H. Haindl; Victor Rocha

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: English
• Weight: 876 KB
• Volume: 135
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041350310

✦ Synopsis

Calcium-binding (-dependent) proteins (CBPs) associated with the spreading of mammary epithelial cell cultures have been identified as various calelectrins and calpactins (p36). In immunoblot analysis, the CBPs of 30-36 kD and 68-70 kD variously react with different calelectrin and calpactin I monomerip36 antisera. The same immunoreactive proteins were shown to be present in virgin mammary glands and collagen gel mouse mammary epithelial cell cultures. The mammary CBPs show extensive immunochemical relatedness; however, they fail to show cross-reaction with antiserum to calpactin II (lipocortin) antiserum. These immunoreactive CBPs comigrate in electrophoresis with "S-methionine-labeled CBPs isolated from mammary epithelial cell cultures. Unlike calmodulin, the mammary CBPs that correspond to calelectrins and calpactin I monomerip36 are not stable to thermal denaturation. The mammary CBPs bind to epithelial cell membranes in a Ca'+-dependent manner and are differentially released from ruptured cells, compared with calmodulin, suggesting subcellular localization. Phenothiazineagarose and phenylagarose are equivalent in their ability to bind the mammary CBPs. Thus, mammary gland CBPs of 30-36 kD and 68-70 kD have been shown to be related or equivalent to the calelectrins and to calpactin I monomerip36. Since these proteins are known to bind CaL+, we conclude that the mammary gland CBPs are also Ca'+-binding proteins. The mammary gland CBPs are immunologically related and probably represent members of a larger family of related proteins.