Multiple regions within the coxsackievirus and adenovirus receptor cytoplasmic domain are required for basolateral sorting

The coxsackievirus and adenovirus receptor (CAR) mediates attachment and in fection by coxsackie B viruses and many adenoviruses. In human airway epith elia, as well as in transfected Madin-Darby canine kidney cells, CAR is exp ressed exclusively on the basolateral surface. Variants of CAR that lack th e cytoplasmic domain or are attached to the cell membrane by a glycosylphos phatidylinositol anchor are expressed on both the apical and basolateral su rfaces, We have examined the localization of CAR variants with progressive truncations of the cytoplasmic domain, as well as with mutations that ablat e a potential PDZ (PSD95/dlg/ZO-1) interaction motif and a putative tyrosin e-based sorting signal. In addition, we have examined the targeting of two murine CAR isoforms, with different C-terminal sequences. The results sugge st that multiple regions within the CAR cytoplasmic domain contain informat ion that is necessary for basolateral targeting.