Caco-2 cell differentiation is associated with a decrease in Stat protein levels and binding

Novel proteins of the Stat (signal transducers and activators of transcription) family have been associated with proliferation and differentiation of certain cells; the role of these transcription factors in gut differentiation has not been examined. The purpose of this study was to determine whether the cellular levels and actual binding of the Stat proteins are altered with intestinal differentiation using the Caco-2 cell line that spontaneously differentiates to a small bowel phenotype after confluent. We found that both Stat3 and Stat5 protein levels st ere increased in preconfluent and confluent Caco-2 cells; levels then decreased with postconfluency. Mobility shift assays demonstrated maximal binding of Stat3 and Stat5 at confluency and, similar to protein levels, binding activity decreased with postconfluency. The intestinal differentiation marker gene sucrase-isomaltase was increased by postconfluent day 1 with maximal levels by day 6. The progressive decrease of Stat3 and Stat5 protein levels and binding activity, occurring at a time associated with increased Caco-2 cell differentiation, suggests that a decrease in the cellular levels of these proteins may potentially play a role in subsequent intestinal cell differentiation. Delineating the cellular mechanisms responsible for intestinal differentiation is crucial to a better understanding of both normal gut development and aberrant gut growth.