A novel adhesive complex at the base of intestinal microcilli
Intestinal epithelial cells form dense arrays of microvilli at the apical membrane to enhance their functional capacity. Microvilli contain a protocadherin-based intermicrovillar adhesion complex localized at their tips which regulates microvillar length and packaging. Here, we identify a second adhesive complex in microvilli of intestinal epithelial cells. This complex is localized at the basal region of microvilli and consists of the adhesion molecule TMIGD1, the phosphoprotein EBP50 and the F-actin - plasma membrane cross-linking protein ezrin. Ternary complex formation requires unmasking of the EBP50 PDZ domains by ezrin binding and is strongly enhanced upon mutating Ser162 located in PDZ domain 2 of EBP50. Dephosphorylation of EBP50 at S162 is mediated by PP1, a serine/threonine phosphatase localized at the microvillar base and involved in ezrin phosphocycling. Importantly, the binding of EBP50 to TMIGD1 enhances the dynamic turnover of EBP50 at microvilli in a Ser162 phosphorylation-dependent manner. We identify an adhesive complex at the microvillar base and propose a potential mechanism that regulates microvillar dynamics in enterocytes.