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

Abstract

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.

• Authors: G Bultynck, P De Smet, A F Weidema, M Ver Heyen, K Maes, G Callewaert, L Missiaen, J B Parys, H De Smedt
• Journal: The Journal of physiology (J Physiol) Vol. 525 Pt 3 Pg. 681-93 (Jun 15 2000) ISSN: 0022-3751 [Print] England
• PMID: 10856121 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antiprotozoal Agents
• Calcium Channels
• Enzyme Inhibitors
• ITPR1 protein, human
• Immunosuppressive Agents
• Inositol 1,4,5-Trisphosphate Receptors
• Ionophores
• Oxalates
• Phosphodiesterase Inhibitors
• Receptors, Cytoplasmic and Nuclear
• Spermine
• Calcimycin
• Caffeine
• Thapsigargin
• Ivermectin
• immunomycin
• Calcium-Transporting ATPases
• Calcium
• Sirolimus
• Tacrolimus

Topics

• Animals
• Antiprotozoal Agents (pharmacology)
• Aorta (cytology)
• B-Lymphocytes (cytology)
• Biological Transport (drug effects, physiology)
• Caffeine (pharmacology)
• Calcimycin (pharmacology)
• Calcium (pharmacokinetics)
• Calcium Channels (physiology)
• Calcium Signaling (drug effects, 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, enzymology)
• Muscle, Smooth, Vascular (chemistry, cytology, enzymology)
• Neuroblastoma
• Oxalates (pharmacology)
• Phosphodiesterase Inhibitors (pharmacology)
• Rats
• Receptors, Cytoplasmic and Nuclear (physiology)
• Sirolimus (pharmacology)
• Spermine (pharmacology)
• Tacrolimus (analogs & derivatives, pharmacology)
• Thapsigargin (pharmacology)
• Tumor Cells, Cultured