Influence of aging and caloric restriction on activation of Ras/MAPK, calcineurin, and CaMK-IV activities in rat T cells.
The signaling cascade mediated by Ras (p21ras) and MAPK (mitogen-activated protein kinase) and calcium/calmodulin regulating enzymes, calcineurin (CaN) and CaMK-IV, are considered to be essential for T-cell growth and function. In the present study, the effect of aging and caloric restriction (CR) on the induction of Ras and MAPK activation by concanavalin A (ConA) was studied. Splenic T cells were isolated from young (4-6 months) and old (22-24 months) rats that had free access to food (control group), and from caloric restricted old (22-24 months) rats that beginning at 6 weeks of age were fed 60%(40% caloric restriction) of the diet consumed by the control rats. We found that the induction of Ras activity in T cells isolated from control old rats was lower (P<0.001) than that in control young rats. However, the levels of Ras activity in T cells isolated from CR old rats were similar to the levels in the age-matched control rats. The induction of MAPK activity in T cells isolated from control old rats and CR old rats was significantly less than in T cells isolated from control young rats, and caloric restriction significantly (P<0.05) reduced the age-related decline in MAPK activation. We also measured the induction of CaN and CaMK-IV activities by ConA in T cells from control young and old and CR old rats. The induction of both CaN and CaMK-IV activity decreased with age. Caloric restriction significantly (P<0.05) reduced the age-related decline in CaN activity, but had no significant effect on CaMK-IV activity. The changes in Ras/MAPK activation and in CaN and CaMK-IV activity with age or with CR were not associated with alterations in their corresponding protein levels. Thus, caloric restriction has a differential effect on the activation of the upstream signaling molecules that are altered with age.
Pahlavani
M A
MA
Geriatric Research, Education, and Clinical Center, Audie L. Murphy Veterans Hospital, and Department of Physiology, University of Texas Health Science Center, San Antonio 78284, USA. Pahlavani@uthscsa.edu
Vargas
D M
DM
D000375:Aging / Q000378:metabolism*; D000818:Animals; D019703:Calcineurin / Q000378:metabolism*; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002149:Energy Intake; D004789:Enzyme Activation; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D013601:T-Lymphocytes / Q000201:enzymology*
D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517686:Camk4 protein, rat; D020928:Mitogen-Activated Protein Kinases; D019703:Calcineurin; D016283:Proto-Oncogene Proteins p21(ras)