Lysophosphatidic acid-induced changes in cAMP profiles in young and senescent human fibroblasts as a clue to the ageing process.
This study attempts to elucidate the molecular mechanisms underlying the ageing-dependent cAMP profiles in human diploid fibroblasts stimulated by lysophosphatidic acid (LPA). In senescent cells, LPA-dependent Gialpha activation was reduced, with a consequent reduction in Gi-suppressed cAMP levels, without alterations in the levels of Gialpha proteins. In young cells, when Gialpha activity was inhibited by pertussis toxin pretreatment, or when its expression was blocked by siRNA, the pattern of changes in cAMP levels in response to LPA was similar to that seen in senescent cells. An increase in protein kinase C (PKC)-dependent isoforms of adenylyl cyclase (AC) types II, IV, and VI was also observed in these senescent fibroblasts. In senescent cells treated with PKC-specific inhibitors, bis-indolylmaleimide, Gö6976, rottlerin, and PKCvarepsilonV1, LPA-induced cAMP accumulation was inhibited, indicating that increased ACs in response to LPA occur via the activation of protein kinase Cs. When the expression of AC II, IV, and VI was blocked by siRNA in senescent fibroblasts, LPA-induced cAMP accumulation was also blocked. These results suggest that the senescence-associated increase of cAMP levels after LPA treatment is associated with reduced Gialpha, increased AC II, IV, and VI proteins, and PKC-dependent stimulation of their activities and provide an explanation for the age-dependent differences in cAMP-related physiological responses.
Jang
Ik-Soon
IS
Department of Biochemistry and Molecular Biology, Ageing and Apoptosis Research Center, Seoul National University College of Medicine, Chongno-gu, South Korea.
Rhim
Ji-Heon
JH
Kim
Kyung-Tae
KT
Cho
Kyung A
KA
Yeo
Eui-Ju
EJ
Park
Sang Chul
SC
D000098:Acetophenones / Q000494:pharmacology; D000375:Aging; D001578:Benzopyrans / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D002460:Cell Line; D016922:Cellular Senescence; D000242:Cyclic AMP / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008246:Lysophospholipids / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D049368:Receptors, Lysophosphatidic Acid / Q000378:metabolism
D000098:Acetophenones; D001578:Benzopyrans; D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D008246:Lysophospholipids; D034741:RNA, Small Interfering; D049368:Receptors, Lysophosphatidic Acid; C081021:Go 6976; D000242:Cyclic AMP; C085746:rottlerin; C032881:lysophosphatidic acid