The calpains, a family of calcium-requiring intracellular proteases, are proposed regulators
of cell proliferation. However, ablation of the calpain small subunit gene necessary for
function of the conventional calpains did not result in decreased rate of proliferative growth
of mouse stem cells under routine culture conditions. To address the reasons for this
discrepancy, Chinese hamster ovary cell lines were established that overexpress the
calpain inhibitor protein, calpastatin, under control of the ecdysone congener, ponasterone …