The alpha 1 and alpha 2 polypeptides of the dihydropyridine-sensitive calcium channel differ in developmental expression and tissue distribution.
The dihydropyridine (DHP) binding complex isolated from skeletal muscle contains two large proteins, alpha 1 and alpha 2, and at least two smaller polypeptides. The alpha 1 subunit has a primary structure expected for ion channels and is a functional component of a DHP-sensitive, voltage-activated calcium channel. The functions of the alpha 2 protein and the smaller polypeptides are unknown. We prepared monoclonal antibodies to the alpha 1 and alpha 2 polypeptides and studied the developmental appearance and tissue distribution of these two proteins. In rat skeletal muscle, the levels of alpha 1 are quite low during the first 10 days after birth, then rise dramatically, and, by day 20, approach those found in adult muscle. In direct contrast, alpha 2 is present in substantial amounts in rat muscle at birth and increases only slightly during this same period of development. Furthermore, alpha 1 is detected only in skeletal muscle, whereas alpha 2 is present in a variety of tissues. These results provide evidence for the segregation of these two polypeptides and suggest that the function of alpha 2 is not limited to that associated with the DHP-sensitive calcium channel.
Morton
M E
ME
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03756.
Froehner
S C
SC
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D004095:Dihydropyridines / Q000378:metabolism; D005786:Gene Expression Regulation; D051379:Mice; D008807:Mice, Inbred BALB C; D024510:Muscle Development; D009132:Muscles / Q000378:metabolism; D009928:Organ Specificity; D011978:Receptors, Nicotinic / Q000032:analysis / Q000235:genetics* / Q000276:immunology
D000911:Antibodies, Monoclonal; D015220:Calcium Channels; D004095:Dihydropyridines; D011978:Receptors, Nicotinic; C038806:1,4-dihydropyridine; D002118:Calcium