AGE-DEPENDENT CHANGES IN TRANSMEMBRANE SIGNALING - IDENTIFICATION OF G-PROTEINS IN HUMAN-LYMPHOCYTES AND POLYMORPHONUCLEAR LEUKOCYTES

In human neutrophils (PMNLs) we found that in the elderly IP3 formatio n was significantly decreased compared to that of young subjects. For FMLP receptor binding affinity and number no measurable differences oc curred upon ageing, studying both the low or the high affinity recepto rs. The amount of ADP-ribosylated G proteins, catalysed by pertussis t oxin (PT) or cholera toxin (CT), was significantly increased in PMNLs of the elderly. In lymphocytes, the PT-catalysed ADP ribosylation of G proteins was also increased with ageing, while the CT-catalysed ribos ylation was decreased. The autoradiogram of [P-32]ADP-ribosylated prot eins by CT in lymphocytes of young individuals showed a major polypept ide of 40,000 M(r). In contrast, in lymphocytes of the elderly, the ma jor polypeptide was 45,000 M(r). In PMNLs, CT labelled quite strongly the 45,000 M(r) band, mainly in the elderly. When PT was used, no age- related pattern changes could be demonstrated, while differences could be observed between the two types of cells. The use of antiserum P680 (G(alphacommon) showed no age-related pattern changes, while the inte nsity of the labelled proteins varies with age and cell type. The anti serum U46 (G(oalpha) could identify in lymphocytes of young subjects t wo polypeptides 68,000 and 41,000 M(r). The prominent polypeptide in l ymphocytes of the elderly was the 70,000 M(r) and no other polypeptide s could be recognized. In PMNLs of young subjects the U46 and serum id entified a range of species. In PMNLs of the elderly all these bands w ere weakly labelled. The present data indicate changes in the pattern and the quantity of G proteins in lymphocytes and PMNLs of elderly sub jects.