Limited proteolysis of the coxsackievirus and adenovirus receptor (CAR) on HeLa cells exposed to trypsin

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Abstract
Trypsin treatment of HeLa cells results in a limited proteolysis of the coxsackievirus and adenovirus receptor (CAR) after which the cleaved CAR remains cell‐associated and tryptic peptides remain associated through disulfide bonds. Trypsin‐treated HeLa cells remain susceptible to infection with coxsackievirus B and produce progeny virus at 8 h post‐infection in amounts comparable to cells with intact CAR. HeLa cells remove the proteolysed CAR within 15 h and require over 24 h to restore intact CAR to control levels. As turnover is relatively slow, physiological functions that require intact CAR protein may be compromised for more than 24 h following trypsin treatment. Moreover, since removal of proteolysed CAR proceeds at more than twice the replacement rate, trypsin treatment disrupts the receptor‐per‐cell steady state for at least 24 h.