TY - JOUR AU - Sun, Tao AU - Turk, Vito AU - Turk, Boris AU - KOPITAR-JERALA, Natasha PY - 2012 M3 - Original Research TI - Increased expression of stefin B in the nucleus of T98G astrocytoma cells delays caspase activation JO - Frontiers in Molecular Neuroscience UR - https://www.frontiersin.org/articles/10.3389/fnmol.2012.00093 VL - 5 SN - 1662-5099 N2 - Stefin B (cystatin B) is an endogenous inhibitor of cysteine proteinases localized in the nucleus and the cytosol. Loss-of-function mutations in the stefin B gene (CSTB) gene were reported in patients with Unverricht-Lundborg disease (EPM1). Our previous results showed that thymocytes isolated from stefin B-deficient mice are more sensitive to apoptosis induced by the protein kinase C (PKC) inhibitor staurosporin (STS) than the wild-type control cells. We have also shown that the increased expression of stefin B in the nucleus of T98G astrocytoma cells delayed cell cycle progression through the S phase. In the present study we examined if the nuclear or cytosolic functions of stefin B are responsible for the accelerated induction of apoptosis observed in the cells from stefin B-deficient mice. We have shown that the overexpression of stefin B in the nucleus, but not in the cytosol of astrocytoma T98G cells, delayed caspase-3 and -7 activation. Pretreatment of cells with the pan-caspase inhibitor z-Val-Ala-Asp(OMe)-fluoromethylketone completely inhibited caspase activation, while treatment with the inhibitor of calpains- and papain-like cathepsins (2S,3S)-trans-epoxysuccinyl-leucylamido-3-methyl-butane ethyl ester did not prevent caspase activation. We concluded that the delay of caspase activation in T98G cells overexpressing stefin B in the nucleus is independent of cathepsin inhibition. ER -