Incorporation of [3H]leucine into an actin-like protein in response to 1,25-dihydroxycholecalciferol in chick intestinal brush borders

Abstract

1,25-Dihydroxycholecalciferol very rapidly stimulates the incorporation of [4,5-3H]leucine into at least 2 proteins of the chick intestinal mucosal cells. The smaller of the 2 proteins has MW .apprx. 42,000, very similar to actin. Other properties of this protein were investigated, including its solubility in salt solution and its behavior on gel electrophoresis and isoelectric focusing. In all cases the 1,25-dihydroxycholecalciferol-stimulated protein was indistinguishable from intestinal actin. The brush borders of mucosal cells contain both .beta.- and .gamma.-actin in approximately equal amounts and both forms of the protein appear to be affected by the hormone. One of the earliest actions of 1,25-dihydroxycholecalciferol apparently is to stimulate the incorporation of leucine into .beta.- and .gamma.-actin of the mucosal cells or into 2 proteins very like them.