IDENTIFICATION OF PP1 CATALYTIC SUBUNIT ISOTYPES PP1-GAMMA-1, PP1-DELTA AND PP1-ALPHA IN VARIOUS RAT-TISSUES

cDNA clones for 4 rat protein phosphatase 1 (PP1) catalytic subunit isotypes, PP1α, PP1γ1, PP1γ2 and PP1δ, were isolated (K. Sasaki et al., Jpn. J. Cancer Res. 81, 1272-1280, 1990). Antibodies were raised to determine the physiological functions of 4 isotypes. Among these isotypes, the PP1γ2 protein was detected specifically in rat testis (H. Shima et al., Adv. Prot. Phosphatases, vol. 7, in press). On the other hand, PP1γ1, PP1δ and PP1α were detected as 36kDa, 37kDa and 38kDa proteins in several rat organs by immunoblot analysis. All three isotypes were found in both soluble and particulate fractions. PP1γ1 was predominant in the brain and PP1δ in the brain, lung and small intestine, but the levels of both were low in the liver and muscle. It became evident that PP1α was not a predominant isotype in any tissue examined. © 1993 Academic Press, Inc.