Tissue distribution of GAP1 and GAP1: Two inositol 1,3,4,5-tetrakisphosphate-binding proteins

Two members of the GAP1 family, GAP1^IP4BP and GAP1^m, have been shown to bind the putative second messenger Ins(1,3,4,5)P₄ with high affinity and specificity, though other aspects of their behaviour suggest that in vivo, whereas GAP1^IP4BP may function as an Ins(1,3,4,5)P₄ receptor, GAP1^m may be a receptor for the lipid second messenger PtdIns(3,4,5)P₃. As a step towards clarifying their cellular roles, we describe here how we have raised and characterised antisera that are specific for the two proteins, and used these to undertake a comprehensive study of their tissue distribution. Both proteins are widely expressed, but there are several clear differences between them in the tissues that show the highest levels of expression.