Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P21817 (RyR1)
 1,154 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ryanodine receptors (RyRs) are intracellular channels that regulate the release of Ca2+ from the endoplasmic reticulum of many cell types. The RyRs are physically associated with FK506-binding proteins (FKBPs); immunophilins, with cis-trans peptidyl-prolyl isomerase activity. FKBP12 copurifies with RyR1 (skeletal isoform) and modulates its gating. A different form of FKBP with a slightly higher molecular weight copurifies with RyR2 (cardiac isoform). Previous studies have demonstrated that FKBP stablizes gating of the skeletal Ca(2+)-release channel. In the present study, we measured the activity of cardiac RyRs incorporated into planar lipid bilayers to show that rapamycin, a drug that inhibits the prolyl isomerase activity of FKBP and dissociates FKBP from the RyR, increases the open probability and reduces the current amplitude of cardiac muscle Ca(2+)-release channels. These experiments show for the first time that submicromolar concentrations of rapamycin can alter channel function. Our results provide support for the hypotheses that FKBP functionally associates with the RyR and that the immunosuppressant drug, rapamycin, alters the function of both cardiac and skeletal muscle isoforms of the Ca(2+)-release channel. Our findings suggest that FKBP-dependent modulation of channel function may be generally applicable to all members of the intracellular Ca(2+)-release channel family and that FKBPs may play important regulatory roles in many cell processes, ranging from long-term depression in neurons to contractility in cardiomyocytes.
 ...
PMID:Effects of rapamycin on ryanodine receptor/Ca(2+)-release channels from cardiac muscle. 863 49

The FK506 binding protein (FKBP12) is the cytosolic receptor for the immunosuppressant drugs FK506 and rapamycin. Recently, we have shown that FKBP12 copurifies with the ryanodine receptor (RyR), a 565,000-Da protein with four subunits that form the intracellular calcium release channels of the sarcoplasmic reticulum and endoplasmic reticulum. To identify the cellular function of FKBP12, in the absence of the ligands rapamycin and FK506, we coexpressed RyR and FKBP12 in insect cells. By measuring the single-channel properties of the RyR-FKBP complex reconstituted into planar lipid bilayers, we showed that FKBP12 modulates channel gating by decreasing channels with subconductance states, decreasing open probability after caffeine activation, and increasing mean open time. These effects were reversed by adding FK506 or rapamycin, both of which inhibit FKBP12 isomerase activity and dissociate the FKBP-RyR complex. These studies provided a natural cellular (ligand-independent) function for FKBP12 and established that the functional calcium release channel complex includes FKBP12. We also expressed recombinant RyR1 in Xenopus laevis oocytes that lack FKBP12. Functional studies showed that the properties of the cloned RyR1, expressed in oocytes, were comparable to those of the native RyR1. These studies showed that FKBP12 is not required for tetrameric formation of the channel structure or for insertion into an intracellular calcium-containing membrane. Both insect cells (Sf9) and Xenopus oocytes are excellent models for heterologous expression of FKBP12 and RyR. Combined with determination of the single-channel properties of the resulting complex reconstituted into planar lipid bilayers, these approaches are well suited to the study of the role of FKBP12 as a modulator of calcium channel function.
 ...
PMID:Immunophilin Modulation of Calcium Channel Gating 881 65

Intracellular Ca2+-release channels on the sarcoplasmic reticulum of striated muscle [ryanodine receptors (RyRs)] and on the endoplasmic reticulum of almost all types of cells [inositol 1,4,5-trisphosphate receptors (IP3Rs)] comprise a unique family of molecules that are structurally and functionally distinct from all other known ion channels. These channels play crucial roles in Ca2+-mediated signaling that triggers excitation-contraction coupling, T-lymphocyte activation, fertilization, and many other cellular functions. Three forms of RyR have been identified: RyR1, expressed predominantly in skeletal muscle; RyR2, expressed predominantly in cardiac muscle; and RyR3, expressed in specialized muscles and nonmuscle tissues including the brain. RyR channels are tetramers composed of four subunits each with a molecular mass of approximately 560,000 Da. The tetrameric structures of RyR1 and RyR2 are stabilized by a channel-associated protein known as the FK506 binding protein (FKBP). FKBP is the cytosolic receptor for the immunosuppressant drugs FK506 and rapamycin that inhibit the prolyl isomerase activity of FKBP and can dissociate FKBP from RyRs. Rapamycin and FK506 increase the sensitivity of RyRs to agonists such as caffeine and could be a cause of cardiac dysfunction associated with high-dose immunosuppressant therapy by promoting leakage of Ca2+ from the sarcoplasmic reticulum. The role of prolyl isomerase activity of FKBP in regulating RyR function remains uncertain, and several models have been proposed that could explain how the channel is modulated by its association with FKBP. Three forms of IP3Rs (types 1, 2 and 3) have been characterized by cDNA cloning. Most cells have at least one form of IP3R, and many express all three types. Like RyRs, the IP3R channels are tetramers composed of four subunits (approximately 300,000 Da each). IP3R1 function is regulated by at least two major cellular signaling pathways: the second messenger IP3 activates the channel, and phosphorylation by nonreceptor protein tyrosine kinases (e.g., Fyn) increase its open probability. During end-stage human heart failure, RyR2 mRNA and protein are downregulated, whereas IP3R1 is upregulated, suggesting that altered Ca2+-release channel levels may contribute to defects in Ca2+ homeostasis. Cells that are deficient in IP3R1 exhibit defective T cell-receptor signaling and thus cannot be activated by T cell-receptor stimulation. IP3R1-deficient cells are also resistant to induced apoptosis. Thus RyRs and IP3Rs play critical roles in fundamental and diverse signaling phenomena that include excitation-contraction coupling, T-cell activation, and programmed cell death.
 ...
PMID:Intracellular calcium-release channels: regulators of cell life and death. 912 14

FKBP12, a cis-trans prolyl isomerase that binds the immunosuppressants FK506 and rapamycin, is ubiquitously expressed and interacts with proteins in several intracellular signal transduction systems. Although FKBP12 interacts with the cytoplasmic domains of type I receptors of the transforming growth factor-beta (TGF-beta) superfamily in vitro, the function of FKBP12 in TGF-beta superfamily signalling is controversial. FKBP12 also physically interacts stoichiometrically with multiple intracellular calcium release channels including the tetrameric skeletal muscle ryanodine receptor (RyR1). In contrast, the cardiac ryanodine receptor, RyR2, appears to bind selectively the FKBP12 homologue, FKBP12.6. To define the functions of FKBP12 in vivo, we generated mutant mice deficient in FKBP12 using embryonic stem (ES) cell technology. FKBP12-deficient mice have normal skeletal muscle but have severe dilated cardiomyopathy and ventricular septal defects that mimic a human congenital heart disorder, noncompaction of left ventricular myocardium. About 9% of the mutants exhibit exencephaly secondary to a defect in neural tube closure. Physiological studies demonstrate that FKBP12 is dispensable for TGF-beta-mediated signalling, but modulates the calcium release activity of both skeletal and cardiac ryanodine receptors.
 ...
PMID:Cardiac defects and altered ryanodine receptor function in mice lacking FKBP12. 946 Dec 16

The ryanodine receptor/calcium release channel (RyR1) of sarcoplasmic reticulum from rabbit skeletal muscle terminal cisternae (TC) contains four tightly associated FK506-binding proteins (FKBP12). Dissociation and reconstitution studies have shown that RyR1 can be modulated by FKBP12, which helps to maintain the channel in the quiescent state. In this study, we found that the association of FKBP with RyR1 of skeletal muscle is common to each of the five classes of vertebrates. TC from skeletal muscle representing animals from different vertebrates, i.e. mammals (rabbit), birds (chicken), reptiles (turtle), fish (salmon and rainbow trout), and amphibians (frog), were isolated. For each, we find the following: 1) FKBP12 is localized to the TC (there are four FKBP binding sites/ryanodine receptor); 2) soluble FKBP exchanges with the bound form on RyR1 of TC; 3) release of FKBP from terminal cisternae by drug (FK590) treatment leads to a significant reduction in the net calcium loading rate, consistent with channel activation (the calcium loading rate is restored to the control value by reconstitution with FKBP12); and 4) RyR1 of skeletal muscle TC can bind to and exchange with either FKBP12 or FKBP12.6 (FKBP12.6 is the novel FKBP isoform found selectively associated with RyR2 of dog cardiac sarcoplasmic reticulum). We conclude that FKBP is an integral part of the RyR1 of skeletal muscle in each of the classes of vertebrate animals. The studies are consistent with a role for FKBP in skeletal muscle excitation-contraction coupling.
 ...
PMID:FK-binding protein is associated with the ryanodine receptor of skeletal muscle in vertebrate animals. 985 7

The marine sponge Ianthella basta synthesizes at least 25 tetrameric bromotyrosine structures that possess a stringent structural requirement for modifying the gating behavior of ryanodine-sensitive Ca(2+) channels (ryanodine receptors) (RyR)). Bastadin 5 (B5) was shown to stabilize open and closed channel states with little influence on the sensitivity of the channel to activation by Ca(2+) (Mack, M. M., Molinski, T. F., Buck, E. D., and Pessah, I. N. (1994) J. Biol. Chem. 269, 23236-23249). In the present paper, we utilize single channel analysis and measurements of Ca(2+) flux across the sarcoplasmic reticulum to identify bastadin 10 (B10) as the structural congener responsible for dramatically stabilizing the open conformation of the RyR channel, possibly by reducing the free energy associated with closed to open channel transitions (DeltaG*c --> o). The stability of the channel open state induced by B10 sensitized the channel to activation by Ca(2+) to such an extent that it essentially obviated regulation by physiological concentrations of Ca(2+) and relieved inhibition by physiological Mg(2+). These actions of B10 were produced only on the cytoplasmic face of the channel, were selectively eliminated by pretreatment of channels with FK506 or rapamycin, and were reconstituted by human recombinant FKBP12. The actions of B10 were found to be reversible. A structure-activity model is proposed by which substitutions on the Eastern and Western hemispheres of the bastarane macrocycle may confer specificity toward the RyR1-FKBP12 complex to stabilize either the closed or open channel conformation. These results indicate that RyR1-FKBP12 complexes possesses a novel binding domain for phenoxycatechols and raise the possibility of molecular recognition of an endogenous ligand.
 ...
PMID:Bastadin 10 stabilizes the open conformation of the ryanodine-sensitive Ca(2+) channel in an FKBP12-dependent manner. 1055 14

Excitation-contraction (EC) coupling in muscle requires the activation of intracellular calcium release channels (CRC). Four type 1 ryanodine receptor (RyR1) molecules form each tetrameric CRC. Each RyR1 contains a binding site for the FK506 binding protein (FKBP12), a cis-trans peptidyl-prolyl isomerase that is required for coordinated gating of the four RyR1 subunits comprising the channel. When FKBP12 is bound to RyR1, it stabilizes the four subunits that form each CRC. We propose that binding of one FKBP12 to each RyR1 lowers the energy of twisted-amide peptidyl-prolyl bonds and stabilizes RyR1 in a conformation that permits coordinated gating of the four RyR1 subunits.
 ...
PMID:FKBP12 modulates gating of the ryanodine receptor/calcium release channel. 1060 43

We examined the effect of low concentrations of H(2)O(2) on the Ca(2+)-release channel/ryanodine receptor (RyR) to determine if H(2)O(2) plays a physiological role in skeletal muscle function. Sarcoplasmic reticulum vesicles from frog skeletal muscle and type 1 RyRs (RyR1) purified from rabbit skeletal muscle were incorporated into lipid bilayers. Channel activity of the frog RyR was not affected by application of 4.4 mM (0.02%) ethanol. Open probability (P(o)) of such ethanol-treated RyR channels was markedly increased on subsequent addition of 10 microM H(2)O(2). Increase of H(2)O(2) to 100 microM caused a further increase in channel activity. Application of 4.4 mM ethanol to 10 microM H(2)O(2)-treated RyRs activated channel activity. Exposure to 10 or 100 microM H(2)O(2) alone, however, failed to increase P(o). Synergistic action of ethanol and H(2)O(2) was also observed on the purified RyR1 channel, which was free from FK506 binding protein (FKBP12). H(2)O(2) at 100-500 microM had no effect on purified channel activity. Application of FKBP12 to the purified RyR1 drastically decreased channel activity but did not alter the effects of ethanol and H(2)O(2). These results suggest that H(2)O(2) may play a pathophysiological, but probably not a physiological, role by directly acting on skeletal muscle RyRs in the presence of ethanol.
 ...
PMID:H(2)O(2) and ethanol act synergistically to gate ryanodine receptor/calcium-release channel. 1102 84

We investigated the interaction of the 12 kDa FK506-binding protein (FKBP12) with two ryanodine-receptor isoforms (RyR1 and RyR3) and with two myo-inositol 1,4,5-trisphosphate (IP3) receptor isoforms (IP3R1 and IP3R3). Using glutathione S-transferase (GST)-FKBP12 affinity chromatography, we could efficiently extract RyR1 (42+/-7% of the solubilized RyR1) from terminal cisternae of skeletal muscle as well as RyR3 (32+/-4% of the solubilized RyR3) from RyR3-overexpressing HEK-293 cells. These interactions were completely abolished by FK506 (20 microM) but were largely unaffected by RyR-channel modulators. In contrast, neither IP3R1 nor IP3R3 from various sources, including rabbit cerebellum, A7r5 smooth-muscle cells and IP3R-overexpressing Sf9 insect cells from Spodoptera frugiperda, were retained on the GST-FKBP12 matrix. Moreover, immunoprecipitation experiments indicated a high-affinity interaction of FKBP12 with RyR1 but not with IP3R1. In order to determine the FKBP12-binding site, we fragmented both RyR1 and IP33R1 by limited proteolysis. We obtained a 45 kDa fragment of RyR1 that bound to the GST-FKBP12 matrix, indicating that it retained all requirements for FKBP12 binding. This fragment was identified by its interaction with antibody m34C and must therefore contain its epitope (amino acids 2756-2803). However, no fragment of IP3R1 was retained on the column. These molecular data are in agreement with the lack of correlation between FKBP12 and IP3R1 expression in various cell types. The observation that FKBP12 did not affect IP3-induced Ca2+ release but reduced caffeine-induced Ca2+ release also indicated that mature IP3R1 and IP3R3, in contrast to RyR1 and RyR3, did not display a specific, high-affinity interaction with FKBP12.
 ...
PMID:Characterization and mapping of the 12 kDa FK506-binding protein (FKBP12)-binding site on different isoforms of the ryanodine receptor and of the inositol 1,4,5-trisphosphate receptor. 1117 Nov 21

FK506 binding protein (FKBP) is a cytosolic receptor for the immunosuppressive drug FK-506. The common isoform, FKBP12, was found to be associated with the calcium release channel (ryanodine receptor 1) of different species of vertebrate skeletal muscle, whereas 12.6, a novel FKBP isoform was found to be associated with canine cardiac ryanodine receptor (ryanodine receptor 2). Until recently, canine cardiac sarcoplasmic reticulum was considered to be the prototype for studying heart RyR2 and its interactions with FKBP. In this study, cardiac microsomes were isolated from diverse vertebrates: human, rabbit, rat, mice, dog, chicken, frog, and fish and were analyzed for their ability to bind or exchange with FKBP isoforms 12 and 12.6. Our studies indicate that RyR2 from seven out of the eight animals contain both FKBP12 and 12.6. Dog is the exception. It can now be concluded that the association of FKBP isoforms with RyR2 is widely conserved in the hearts of different species of vertebrates.
 ...
PMID:FKBP binding characteristics of cardiac microsomes from diverse vertebrates. 1123 59


1 2 3 4 5 Next >>