The regulation of expression of integrin receptors.

The integrins are a family of cell surface receptors that mediate cell-extracellular matrix and cell-cell interactions. The quantities and activities of these receptors are modulated during a wide variety of biological processes. A variety of agents have been found to affect expression of integrins and their function. These include cytokines, hormones, and pharmacologic agents. Mechanisms regulating integrin expression and function include regulation of protein levels by transcriptional or posttranscriptional mechanisms, alteration of protein structure by alternative splicing of mRNA, mobilization to the cell surface of preexisting intracellular stores of integrins, and modulation of receptor activity (inside-out signaling). We review studies that assess the effects of external agents on integrin levels using the cytokine TGFbeta as an example. We also review studies that analyze integrin regulation with an emphasis on the control of integrin gene transcription. This review shows that the strategies for integrin modulation are quite complex. This regulatory sophistication is likely necessary, given the critical role that integrins play in the myriad social interactions of cells.