The intracellular domain of the coxsackievirus and adenovirus receptor differentially influences adenovirus entry

The coxsackievirus and adenovirus receptor (CAR) is a cell adhesion molecule used as a docking molecule by some adenoviruses (AdVs) and group B coxsackieviruses. We previously proposed that the preferential transduction of neurons by canine adenovirus type 2 (CAV-2) is due to CAR-mediated internalization. Our proposed pathway of CAV-2 entry is in contrast to that of human AdV type 5 (HAdV-C5) in non-neuronal cells, where internalization is mediated by auxiliary receptors such as integrins. We therefore asked if in fibroblast-like cells the intracellular domain (ICD) of CAR plays a role in the internalization of the CAV-2 fiber knob (FKCAV), CAV-2, or HAdV-C5 when the capsid cannot engage integrins. Here, we show that in fibroblast-like cells, the CAR ICD is needed for FKCAV entry and efficient CAV-2 transduction, but dispensable for HAdV-C5 and a HAdV-C5 capsid lacking the RGD sequence (an integrin-interacting motif) in the penton. Moreover, the deletion of CAR ICD further impacts CAV-2 intracellular trafficking, highlighting the crucial role of CAR in CAV-2 intracellular dynamics. These data demonstrate that CAR ICD contains sequences important for the recruitment of the endocytic machinery that differentially influences AdV cell entry. IMPORTANCE: Understanding how viruses interact with the host cell surface and reach the intracellular space is of crucial importance for applied and fundamental virology. Here, we compare the role of a cell adhesion molecule (CAR), in the internalization of adenoviruses that naturally infect humans and Canidae. We show that the intracellular domain of CAR differentially regulate AdV entry and trafficking. Our study highlights the mechanistic differences that a receptor can have for two viruses from the same family.