Intracellular Ca2+ pool content is linked to control of cell growth.
A close correlation was observed between intracellular Ca2+ pool depletion and refilling and the onset of DNA synthesis and proliferation of DDT1MF-2 smooth muscle cells. The intracellular Ca2+ pump inhibitors 2,5-di-tert-butyl-hydroquinone (DBHQ) and thapsigargin (TG) specifically emptied identical inositol 1,4,5-trisphosphate (InsP3)-sensitive Ca2+ pools and both arrested cell growth at concentrations corresponding to Ca2+ pump blockade. However, an important distinction was observed between the two inhibitors with respect to their reversibility of action. Upon removal of DBHQ from DBHQ-arrested cells, Ca2+ pools immediately refilled, and 14 hr later cells entered S phase followed by normal cell proliferation; the time for entry into S phase was identical to that for cells released from confluence arrest. Although TG irreversibly blocked Ca2+ pumping and emptied Ca2+ pools, high serum treatment of TG-arrested cells induced recovery of functional Ca2+ pools in 6 hr (via probable synthesis of new pump); thereafter cells proceeded to S phase and normal cell proliferation within the same time period (14 hr) as that following release of DBHQ-arrested cells. The precise relationship between Ca2+ pump blockade and growth arrest indicates that Ca2+ pool emptying maintains cells in a G0-like quiescent state; upon refilling of pools, normal progression into the cell cycle is resumed. It is possible that a specific cell cycle event necessary for G0 to G1 transition depends upon signals generated from the InsP3-sensitive Ca2+ pool.
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Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore 21201.
Bian
J
J
Ghosh
T K
TK
Waldron
R T
RT
Rybak
S L
SL
Gill
D L
DL
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D016257:Fura-2; D006873:Hydroquinones / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D009130:Muscle, Smooth; D013050:Spectrometry, Fluorescence; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors
D000975:Antioxidants; D006873:Hydroquinones; D013729:Terpenes; D015759:Ionomycin; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; C018855:2-tert-butylhydroquinone; D000252:Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2