IP 3 , IP 3 receptor, and cellular senescence

• Published in: American journal of physiology. Renal physiology 2000-04, Vol.278 (4), p.F576-F584
• Main Authors: Huang, Ming-Shyan, Adebanjo, Olugbenga A., Awumey, Emmanuel, Biswas, Gopa, Koval, Antoliy, Sodam, Bali R., Sun, Li, Moonga, Baljit S., Epstein, Joshua, Goldstein, Samuel, Lai, F. Anthony, Lipschitz, David, Zaidi, Mone
• Format: Article
• Language: English
• ISSN: 1931-857X; 1522-1466
• DOI: 10.1152/ajprenal.2000.278.4.F576

Herein we demonstrate that replicative cellular senescence in vitro results in sharply reduced inositol 1,4,5-trisphosphate (IP 3 ) receptor levels, reduced mitogen-evoked IP 3 formation and Ca 2+ release, and Ca 2+ store depletion. Human diploid fibroblasts (HDFs) underwent either 30 mean population doublings [mean population doublings (MPDs) thymidine labeling index (TI) >92% (“young”) or between 53 and 58 MPDs (TI < 28%; “senescent”)]. We found that the cytosolic Ca 2+ release triggered by either ionomycin or by several IP 3 -generating mitogens, namely bradykinin, thrombin, platelet-derived growth factor (PDGF), and epidermal growth factor (EGF), was attenuated markedly in senescent HDFs. Notably, the triggered cytosolic Ca 2+ transients were of a smaller magnitude in senescent HDFs. However, the response latency seen with both PDGF and EGF was greater for senescent cells. Finally, a smaller proportion of senescent HDFs showed oscillations. In parallel, IP 3 formation in response to bradykinin or EGF was also attenuated in senescent HDFs. Furthermore, senescent HDFs displayed a sharply diminished Ca 2+ release response to intracellularly applied IP 3 . Finally, to compare IP 3 receptor protein levels directly in young and senescent HDFs, their microsomal membranes were probed in Western blots with a highly specific anti-IP 3 receptor antiserum, Ab 40 . A ∼260-kDa band corresponding to the IP 3 receptor protein was noted; its intensity was reduced by ∼50% in senescent cells. Thus, we suggest that reduced IP 3 receptor expression, lowered IP 3 formation, and Ca 2+ release, as well as Ca 2+ store depletion, all contribute to the deficient Ca 2+ signaling seen in HDFs undergoing replicative senescence.