Abstract
FK506-binding protein (FKBP12) was originally identified as the cytosolic receptor for the immunosuppressant drugs FK506 and rapamycin. The cellular function of FKBP12, a ubiquitously expressed 12,000-dalton proline isomerase, has been unknown. FKBP12 copurifies with the 565,000-dalton ryanodine receptor (RyR), four of which form intracellular Ca2+ release channels of the sarcoplasmic and endoplasmic reticula. By coexpressing the RyR and FKBP12 in insect cells, we have demonstrated that FKBP12 modulates channel gating by increasing channels with full conductance levels (by > 400%), decreasing open probability after caffeine activation (from 0.63 +/- 0.09 to 0.04 +/- 0.02), and increasing mean open time (from 4.4 +/- 0.6 ms to 75 +/- 41 ms). FK506 or rapamycin, inhibitors of FKBP12 isomerase activity, reverse these stabilizing effects. These results provide the first natural cellular function for FKBP12, and establish that the functional Ca2+ release channel complex includes FKBP12.
Publication types
-
Research Support, Non-U.S. Gov't
-
Research Support, U.S. Gov't, P.H.S.
MeSH terms
-
Animals
-
Caffeine / pharmacology
-
Calcium / metabolism
-
Calcium Channels / genetics
-
Calcium Channels / isolation & purification
-
Calcium Channels / physiology*
-
Carrier Proteins / antagonists & inhibitors
-
Carrier Proteins / genetics
-
Carrier Proteins / isolation & purification
-
Carrier Proteins / physiology*
-
Cell Line
-
Cloning, Molecular
-
Gene Expression
-
Heat-Shock Proteins / antagonists & inhibitors
-
Heat-Shock Proteins / genetics
-
Heat-Shock Proteins / isolation & purification
-
Heat-Shock Proteins / physiology*
-
Ion Channel Gating / drug effects
-
Ion Channel Gating / physiology*
-
Isometric Contraction / drug effects
-
Lipid Bilayers
-
Muscle Proteins / genetics
-
Muscle Proteins / isolation & purification
-
Muscle Proteins / physiology*
-
Polyenes / pharmacology
-
RNA, Messenger / analysis
-
Rabbits
-
Rats
-
Recombinant Proteins / isolation & purification
-
Ruthenium Red / pharmacology
-
Ryanodine / pharmacology
-
Ryanodine Receptor Calcium Release Channel
-
Sarcoplasmic Reticulum / metabolism
-
Sirolimus
-
Tacrolimus / pharmacology
-
Tacrolimus Binding Proteins
Substances
-
Calcium Channels
-
Carrier Proteins
-
Heat-Shock Proteins
-
Lipid Bilayers
-
Muscle Proteins
-
Polyenes
-
RNA, Messenger
-
Recombinant Proteins
-
Ryanodine Receptor Calcium Release Channel
-
Ruthenium Red
-
Ryanodine
-
Caffeine
-
Tacrolimus Binding Proteins
-
Calcium
-
Sirolimus
-
Tacrolimus