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Age-dependent changes in transmembrane signalling: identification of G proteins in human lymphocytes and
1University Medical School of Debrecen, First Department of Medicine, Hungary.
Abstract:
In human neutrophils (PMNLs) we found that in the elderly IP3 formation was significantly decreased compared to that of young subjects. For FMLP receptor binding affinity and number no measurable differences occurred upon ageing, studying both the low or the high affinity receptors. The amount of ADP-ribosylated G proteins, catalysed by pertussis toxin (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 ribosylation was decreased. The autoradiogram of [32P]ADP-ribosylated proteins by CT in lymphocytes of young individuals showed a major polypeptide of 40,000 M(r). In contrast, in lymphocytes of the elderly, the major 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 alpha common) showed no age-related pattern changes, while the intensity of the labelled proteins varies with age and cell type. The antiserum U46 (Go alpha) could identify in lymphocytes of young subjects two polypeptides 68,000 and 41,000 M(r). The prominent polypeptide in lymphocytes of the elderly was the 70,000 M(r) and no other polypeptides could be recognized. In PMNLs of young subjects the U46 and serum identified a range of species. In PMNLs of the elderly all these bands were weakly labelled. The present data indicate changes in the pattern and the quantity of G proteins in lymphocytes and PMNLs of elderly subjects.
Insights
Aging alters G protein function in immune cells. Elderly individuals show decreased IP3 formation and altered G protein ADP-ribosylation patterns in neutrophils and lymphocytes, indicating age-related changes in cellular signaling.
Area of Science:
- Immunology
- Cellular Signaling
- Aging Research
Background:
- G proteins are crucial for cellular signal transduction.
- Age-related changes in immune cell function are well-documented.
- Specific alterations in G protein activity with aging require further investigation.
Purpose of the Study:
- To investigate age-related changes in G protein function in human neutrophils (PMNLs) and lymphocytes.
- To examine the impact of aging on IP3 formation and G protein ADP-ribosylation.
- To characterize age-associated modifications in G protein subunits.
Main Methods:
- Analysis of inositol trisphosphate (IP3) formation in PMNLs.
- Assessment of FMLP receptor binding affinity and number.
- Pertussis toxin (PT) and cholera toxin (CT) catalyzed ADP-ribosylation assays.
- Western blotting using specific antisera (G alpha common, Go alpha) to identify G protein subunits.
Main Results:
- Elderly subjects exhibited significantly decreased IP3 formation in PMNLs compared to young subjects.
- Increased PT- and CT-catalyzed ADP-ribosylation of G proteins in elderly PMNLs.
- Age-dependent alterations in CT-catalyzed ADP-ribosylation patterns and G protein subunit identification in lymphocytes and PMNLs.
- Specific changes observed in Go alpha subunit expression in lymphocytes of the elderly.
Conclusions:
- Aging significantly alters G protein quantity and patterns in human lymphocytes and PMNLs.
- These changes may contribute to age-related functional decline in immune cells.
- Further research is warranted to elucidate the functional consequences of these G protein alterations in aging.