[Age-related alterations on GTP binding proteins in postmortem human brain].

It is important that natural aging-related alterations are characterized to understand disabilities associated with aging. In this study, age-related alterations of GTP binding (G) proteins were examined in membrane preparations from several regions (frontal cortex, temporal cortex, parietal cortex, occipital cortex, caudate nucleus, amygdaloid body) in postmortem human brain. Subjects were free from neurologic or psychiatric disease. The quantity of G proteins (Gs alpha, Gi alpha, Go alpha, Gq alpha, G beta subunit) was determined by immunoblotting with polyclonal antibody (RM/1, AS/7, GC/2, QL, SW/1, respectively). The function of G proteins was examined by photoaffinity GTP analog [azidoanilido GTP (AAGTP)] binding. The immunoreactivities of Gi alpha and Gq alpha subunits were correlated inversely with age in many areas. In caudate nucleus, the GsL alpha (45 kDa) and Go alpha subunit immunoreactivities were decreased with age. And the G beta subunit immunoreactivities showed a negative correlation with age in temporal and occipital cortex areas. However, AAGTP labeling to Gs alpha and Gi/o alpha and the ratio of Gs alpha to Gi/o alpha AAGTP binding showed no age-dependent changes. Our findings suggest that the functional modulation may compensate for quantitative alterations of G proteins with human senescence.