Effects of the immunosuppressant FK506 on intracellular Ca2+ release and Ca2+ accumulation mechanisms

• Published in: The Journal of physiology 2000-06, Vol.525 (3), p.681-693
• Main Authors: Bultynck, Geert, Smet, Patrick, Weidema, A. Frederik, Heyen, Mark, Maes, Karlien, Callewaert, Geert, Missiaen, Ludwig, Parys, Jan B., Smedt, Humbert
• Format: Article
• Language: English
• Subjects: Animals; Antiprotozoal Agents - pharmacology; Aorta - cytology; B-Lymphocytes - cytology; Biological Transport - drug effects; Biological Transport - physiology; Caffeine - pharmacology; Calcimycin - pharmacology; Calcium - pharmacokinetics; Calcium Channels - physiology; Calcium Signaling - drug effects; Calcium Signaling - physiology; Calcium-Transporting ATPases - metabolism; Chickens; Enzyme Inhibitors - pharmacology; Humans; Immunosuppressive Agents - pharmacology; Inositol 1,4,5-Trisphosphate Receptors; Ionophores - pharmacology; Ivermectin - pharmacology; Mice; Microsomes - chemistry; Microsomes - enzymology; Muscle, Smooth, Vascular - chemistry; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - enzymology; Neuroblastoma; Original; Oxalates - pharmacology; Phosphodiesterase Inhibitors - pharmacology; Rats; Receptors, Cytoplasmic and Nuclear - physiology; Sirolimus - pharmacology; Spermine - pharmacology; Tacrolimus - analogs & derivatives; Tacrolimus - pharmacology; Thapsigargin - pharmacology; Tumor Cells, Cultured
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1111/j.1469-7793.2000.t01-1-00681.x

The immunophilin FKBP12 associates with intracellular Ca 2+ channels and this interaction can be disrupted by the immunosuppressant FK506. We have investigated the effect of FK506 on Ca 2+ release and Ca 2+ uptake in permeabilized cell types. Changes in medium free [Ca 2+ ] were detected by the fluorescent Ca 2+ indicator fluo-3 in digitonin-permeabilized SH-SY5Y human neuroblastoma cells, DT40 and R23-11 (i.e. triple inositol 1,4,5-trisphosphate (IP 3 ) receptor knockout cells) chicken B lymphocytes and differentiated and undifferentiated BC 3 H1 skeletal muscle cells. 45 Ca 2+ 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 [Ca 2+ ] corresponding to ∼30% of the Ca 2+ ionophore A23187-induced [Ca 2+ ] rise. This rise in [Ca 2+ ] was not dependent on mitochondrial activity. This FK506-induced [Ca 2+ ] rise was related to the inhibition of the sarcoplasmic/endoplasmic reticulum Ca 2+ -Mg 2+ -ATPase (SERCA) Ca 2+ pump. Oxalate-facilitated 45 Ca 2+ uptake in SH-SY5Y microsomes was inhibited by FK506 with an IC 50 of 19 μ m . The inhibition of the SERCA Ca 2+ pump was not specific since several macrocyclic lactone compounds (ivermectin > FK506, ascomycin and rapamycin) were able to inhibit Ca 2+ uptake activity. FK506 (10 μ m ) did not affect IP 3 -induced Ca 2+ release in permeabilized SH-SY5Y and A7r5 cells, but enhanced caffeine-induced Ca 2+ release via the ryanodine receptor (RyR) in differentiated BC 3 H1 cells. In conclusion, FK506 inhibited active Ca 2+ uptake by the SERCA Ca 2+ pump; in addition, FK506 enhanced intracellular Ca 2+ release through the RyR, but it had no direct effect on IP 3 -induced Ca 2+ release.