Effects of the immunosuppressant FK506 on intracellular Ca2+ release and Ca2+ accumulation mechanisms.
The immunophilin FKBP12 associates with intracellular Ca2+ channels and this interaction can be disrupted by the immunosuppressant FK506. We have investigated the effect of FK506 on Ca2+ release and Ca2+ uptake in permeabilized cell types. Changes in medium free [Ca2+] were detected by the fluorescent Ca2+ indicator fluo-3 in digitonin-permeabilized SH-SY5Y human neuroblastoma cells, DT40 and R23-11 (i.e. triple inositol 1,4,5-trisphosphate (IP3) receptor knockout cells) chicken B lymphocytes and differentiated and undifferentiated BC3H1 skeletal muscle cells. 45Ca2+ fluxes were studied in saponin-permeabilized A7r5 rat smooth muscle cells. Addition of FK506 to permeabilized SH-SY5Y cells led to a sustained elevation of the medium [Ca2+] corresponding to approximately 30 % of the Ca2+ ionophore A23187-induced [Ca2+] rise. This rise in [Ca2+] was not dependent on mitochondrial activity. This FK506-induced [Ca2+] rise was related to the inhibition of the sarcoplasmic/endoplasmic reticulum Ca2+-Mg2+-ATPase (SERCA) Ca2+ pump. Oxalate-facilitated 45Ca2+ uptake in SH-SY5Y microsomes was inhibited by FK506 with an IC50 of 19 microM. The inhibition of the SERCA Ca2+ pump was not specific since several macrocyclic lactone compounds (ivermectin > FK506, ascomycin and rapamycin) were able to inhibit Ca2+ uptake activity. FK506 (10 microM) did not affect IP3-induced Ca2+ release in permeabilized SH-SY5Y and A7r5 cells, but enhanced caffeine-induced Ca2+ release via the ryanodine receptor (RyR) in differentiated BC3H1 cells. In conclusion, FK506 inhibited active Ca2+ uptake by the SERCA Ca2+ pump; in addition, FK506 enhanced intracellular Ca2+ release through the RyR, but it had no direct effect on IP3-induced Ca2+ release.
Bultynck
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Laboratorium voor Fysiologie, K.U.Leuven Campus Gasthuisberg O/N, B-3000 Leuven, Belgium. geert.bultynck@med.kuleuven.ac.be
De Smet
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Weidema
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Ver Heyen
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Maes
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Callewaert
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Missiaen
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Parys
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De Smedt
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D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology; D001011:Aorta / Q000166:cytology; D001402:B-Lymphocytes / Q000166:cytology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002110:Caffeine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000493:pharmacokinetics*; D015220:Calcium Channels / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002645:Chickens; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007476:Ionophores / Q000494:pharmacology; D007559:Ivermectin / Q000494:pharmacology; D051379:Mice; D008861:Microsomes / Q000737:chemistry / Q000201:enzymology; D009131:Muscle, Smooth, Vascular / Q000737:chemistry / Q000166:cytology / Q000201:enzymology; D009447:Neuroblastoma; D010070:Oxalates / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology; D020123:Sirolimus / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology; D016559:Tacrolimus / Q000031:analogs & derivatives / Q000494:pharmacology*; D019284:Thapsigargin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000981:Antiprotozoal Agents; D015220:Calcium Channels; D004791:Enzyme Inhibitors; C506926:ITPR1 protein, human; D007166:Immunosuppressive Agents; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007476:Ionophores; D010070:Oxalates; D010726:Phosphodiesterase Inhibitors; D018160:Receptors, Cytoplasmic and Nuclear; D013096:Spermine; D000001:Calcimycin; D002110:Caffeine; D019284:Thapsigargin; D007559:Ivermectin; C058028:immunomycin; D000252:Calcium-Transporting ATPases; D002118:Calcium; D020123:Sirolimus; D016559:Tacrolimus