PROTEIN L-ISOASPARTYL METHYLTRANSFERASE - DEVELOPMENTALLY-REGULATED GENE-EXPRESSION AND PROTEIN LOCALIZATION IN THE CENTRAL-NERVOUS-SYSTEM OF AGED RAT

We have cloned a cDNA encoding protein L-isoaspartyl methyltransferase (PIMT) and characterized gene expression in the development, maturati on, and the aging process of the central nervous system by RNA blot an alysis, western blot analysis, and immunohistochemistry. PIMT transcri pt was detected in rat embryonic brain and showed a linear up-regulati on during the maturation of the brain and maintained its level in aged rat brain. Immunoblot analysis also supported a linear increase in th e amount of PIMT in the maturation process of rat brains. An immunohis tochemical study showed that PIMT is strongly expressed in neurons and weakly but definitively in glial cells and oligodendrocytes. These im munoreactivities significantly increased in some neurons of the hippoc ampus, cerebral cortex, and the brain stem of aged rat brain. The pres ent results suggest that the expression of PIMT is associated with the amount of racemized/isomerized proteins accumulated during the develo pmental and aging process of the central nervous system.