S100A1 and S100B expression and target proteins in type I diabetes

Calcium receptor proteins are an essential link between hormones that alter intracellular calcium levels and the generation of cellular responses. However, there is no information available regarding the role of calcium receptor proteins, in particular the S100 family, in insulin action and/or diabetes. This study examines the effects of streptozotocin-induced type I diabetes on the expression of the individual S100A1 and S100B isoforms as well as their binding proteins. Diabetes did not increase (or initiate) S100B expression in any non-S100B-expressing tissue (skeletal muscle, heart, kidney, liver, spleen, and pancreas). In all S100B-expressing tissues examined (brain, white fat, and testes), S100B protein levels increased approximately 2-fold while steady state S100B messenger RNA (mRNA) levels decreased. S100A1-expressing tissues exhibited increased (kidney and lung), decreased (skeletal muscle), and unchanged (brain and heart) S100A1 protein levels. While noncoordinate changes in S100A1 protein and steady state mRNA levels were observed in heart, other S100A1-expressing tissues (brain, slow twitch skeletal muscle, and kidney) exhibited coordinate changes in S100A1 protein and steady state mRNA levels. Altogether, these results suggest that the effects of diabetes on S100 expression are isoform as well as tissue-specific. Gel overlay analysis of the S100-binding protein profile revealed both increases and decreases in binding proteins in all tissues examined. In summary, changes in the expression of S100A1, S100B, and S100-binding proteins occur in type I diabetes and represent important molecular events in the effects of insulin/insulin insufficiency on cell function.