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.
