Key result
Ablation of the CAR PDZ-binding motif (CARDeltaGSIV) failed to increase transepithelial resistance to the same degree as wild-type CAR and failed to act as a growth modulator in L-cells.
The CAR PDZ-binding motif is essential for CAR-mediated cell-cell adhesion and growth modulation, interacting with proteins like MAGI-1b, PICK1, and PSD-95.
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CAR PDZ motif ablation impairs barrier function and growth control in L-cells; leaves open in vivo relevance for junctional biology.
The coxsackie and adenovirus receptor (CAR) plays a role in viral infection, maintenance of the junction adhesion complex in polarized epithelia, and modulation of cellular growth properties. As a viral receptor, the C-terminus appears to play no role indicating that the major function of CAR is to tether the virus to the cell. By contrast, the C-terminus is known to play a role in cellular localization and probably has a significant function in CAR-mediated adhesion and cell growth properties. We hypothesized that the CAR PDZ (PSD-95/Disc-large/ZO-1) binding motif interacts with PDZ-domain-containing proteins to modulate the cellular phenotype. CAR was modified by deleting the last four amino acids (CARDeltaGSIV) and evaluated for cell-cell adhesion in polarized primary human airway epithelia and growth characteristics in stably transfected L-cells. Although ablation of the CAR PDZ-binding motif did not affect adenoviral infection, it did have a significant effect both on cell-cell adhesion and on cell growth. Expression of CARDeltaGSIV failed to increase the transepithelial resistance in polarized epithelia to the same degree as wild-type CAR and failed to act as a growth modulator in L-cells. Furthermore, we provide evidence for three new CAR interacting partners, including MAGI-1b, PICK1 and PSD-95. CAR appears to interact with several distinct PDZ-domain-containing proteins and may exert its biological function through these interactions.
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Excoffon et al. (2004) studied this question. Deletion of the last four amino acids of CAR (CARDeltaGSIV) vs. Wild-type CAR was evaluated on Cell-cell adhesion (transepithelial resistance) and cell growth. Ablation of the CAR PDZ-binding motif (CARDeltaGSIV) failed to increase transepithelial resistance to the same degree as wild-type CAR and failed to act as a growth modulator in L-cells.
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