Normalization Of CFTR Brush Border Membrane Trafficking Defects In The Intestines Of Myosin 1a/6 Double Mutant Mice

Abstract

Brush border myosins can move cargo, maintain membrane tension and regulate membrane trafficking. Insertion of CFTR channels into the intestinal brush border membrane (IBBM) is required for anion secretion. The mechanisms of CFTR delivery into the IBBM and its retrieval into trafficking compartments are poorly understood. Myosin 6 (Myo6), the only minus end motor, is the counterpart to the major plus end motor Myosin 1a (Myo1a) in the enterocyte BB. Absence of Myo6 leads to loss of intermicrovillar membrane (MVM) tension, increased surface CFTR and defective apical endocytosis (Traffic. 2007(8):998–1006; JBC, 285 (22), 2010), while absence of Myo1a leads to MVM defects due to lack of plus end tension. Preliminary studies indicate mistargeting of CFTR to the basolateral domain of villus enterocytes in Myo1aKO mice, that is associated with reduced anion transport. We hypothesized that the observed CFTR trafficking defects in Myo6 and Myo1a KO mice would be reversed in Myo1a/6 DKO mice. Preliminary studies reveal normalization of BB architecture in Myo1a/6 DKO mice. Immunolocalization studies of WT129 (WT) and Myo1a/6 DKO intestine reveal normalization of CFTR distribution in all segments. Immunoblots confirmed lack of alteration in CFTR expression between WT and Myo1a/6 DKO mice. Our data suggest that Myo6 works in tandem with Myo1a to regulate the trafficking of CFTR between subapical endosomes and the apical BBM.