Rab11-FIP2 regulates differentiable steps in transcytosis

Transcytosis through the apical recycling system of polarized cells is regulated by Rab11a and a series of Rab11a-interacting proteins. We have identified a point mutant in Rab11 family interacting protein 2 ( Rab11-FIP2) that alters the function of Rab11a-containing trafficking systems. Rab11-FIP2( S229A/R413G) or Rab11-FIP2( R413G) cause the formation of a tubular cisternal structure containing Rab11a and decrease the rate of polymeric IgA transcytosis. The R413G mutation does not alter Rab11-FIP interactions with any known binding partners. Overexpression of Rab11-FIP2( S229A/R413G) alters the localization of a subpopulation of the apical membrane protein GP135. In contrast, Rab11-FIP2( 129-512) alters the localization of early endosome protein EEA1. The distributions of both Rab11-FIP2( S229A/R413G) and Rab11-FIP2( 129-512) were not dependent on the integrity of the microtubule cytoskeleton. The results indicate that Rab11-FIP2 regulates trafficking at multiple points within the apical recycling system of polarized cells.