VPS33B Interacting Protein, Apical Basolateral Polarity Regulator (VIPAR)

VIPAR, had highest priority based on bioinformatic analyses of homology and putative function. Coimmunoprecipitation studies in transfected HEK293 cells confirmed the interaction between overexpressed VPS33B and VIPAR, with formation of functional VPS33B-VIPAR complexes at cytoplasmic organelles that interacted with RAB11A. Knockdown of vipar in zebrafish resulted in biliary excretion and E-cadherin (CDH1) defects similar to those in individuals with ARC syndrome caused by mutation in VPS33B or VIPAR (see MOLECULAR GENETICS section).

Vipar- and Vps33b-deficient mouse inner medullary collecting duct (mIMCD-3) cells expressed membrane proteins abnormally and had structural and functional tight junction defects.