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)

Tryptophan 59 forms the seat of the hydrophobic ligand-binding site in the small immunophilin FKBP12. Mutating this residue to phenylalanine or leucine stabilizes the protein by 2.72 and 2.35 kcal mol(-1), respectively. Here we report the stability data and 1.7 A resolution crystal structures of both mutant proteins, complexed with the immunosuppressant rapamycin. Both structures show a relatively large response to mutation involving a helical bulge at the mutation site and the loss of a hydrogen bond that anchors a nearby loop. The increased stability of the mutants is probably due to a combination of improved packing and an entropic gain at the mutation site. The structures are almost identical to that of wild-type FKBP12.6, an isoform of FKBP12 that differs by 18 residues, including Trp59, in its sequence. Therefore, the structural difference between the two isoforms can be attributed almost entirely to the identity of residue 59. It is likely that in FKBP12-ligand complexes Trp59 provides added binding energy at the active site at the expense of protein stability, a characteristic common to other proteins. FKBP12 associates with the ryanodine receptor in skeletal muscle (RyR1), while FKBP12.6 selectively binds the ryanodine receptor in cardiac muscle (RyR2). The structural response to mutation suggests that residue 59 contributes to the specificity of binding between FKBP12 isoforms and ryanodine receptors.
 ...
PMID:Energetic and structural analysis of the role of tryptophan 59 in FKBP12. 1260 Feb 3

The skeletal muscle sarcoplasmic reticulum (SR) Ca2+ release channel or ryanodine receptor (RyR1) binds four molecules of FKBP12, and the interaction of FKBP12 with RyR1 regulates both unitary and coupled gating of the channel. We have characterized the physiologic effects of previously identified mutations in RyR1 that disrupt FKBP12 binding (V2461G and V2461I) on excitation-contraction (EC) coupling and intracellular Ca2+ homeostasis following their expression in skeletal myotubes derived from RyR1-knockout (dyspedic) mice. Wild-type RyR1-, V246I-, and V2461G-expressing myotubes exhibited similar resting Ca2+ levels and maximal responses to caffeine (10 mm) and cyclopiazonic acid (30 microm). However, maximal voltage-gated Ca2+ release in V2461G-expressing myotubes was reduced by approximately 50% compared with that attributable to wild-type RyR1 (deltaF/Fmax = 1.6 +/- 0.2 and 3.1 +/- 0.4, respectively). Dyspedic myotubes expressing the V2461I mutant protein, that binds FKBP12.6 but not FKBP12, exhibited a comparable reduction in voltage-gated SR Ca2+ release (deltaF/Fmax = 1.0 +/- 0.1). However, voltage-gated Ca2+ release in V2461I-expressing myotubes was restored to a normal level (deltaF/Fmax = 2.9 +/- 0.6) following co-expression of FKBP12.6. None of the mutations that disrupted FKBP binding to RyR1 significantly affected RyR1-mediated enhancement of L-type Ca2+ channel activity (retrograde coupling). These data demonstrate that FKBP12 binding to RyR1 enhances the gain of skeletal muscle EC coupling.
 ...
PMID:FKBP12 binding to RyR1 modulates excitation-contraction coupling in mouse skeletal myotubes. 1270 93

Mitochondrial genetic and metabolic stress causes activation of calcineurin (Cn), NFAT, ATF2, and NFkappaB/Rel factors, which collectively alter the expression of an array of nuclear genes. We demonstrate here that mitochondrial stress-induced activation of NFkappaB/Rel factors involves inactivation of IkappaBbeta through Cn-mediated dephosphorylation. Phosphorylated IkappaBbeta is a substrate for Cn phosphatase, which was inhibited by FK506 and RII peptide. Chemical cross-linking and coimmunoprecipitation show that NFkappaB/Rel factor-bound IkappaBbeta forms a ternary complex with Cn under in vitro and in vivo conditions that was sensitive to FK506. Results show that phosphorylation at S313 and S315 from the COOH-terminal PEST domain of IkappaBbeta is critical for binding to Cn. Mutations at S313/S315 of IkappaBbeta abolished Cn binding, inhibited Cn-mediated increase of Rel proteins in the nucleus, and had a dominant-negative effect on the mitochondrial stress-induced expression of RyR1 and cathepsin L genes. Our results show the distinctive nature of mitochondrial stress-induced NFkappaB/Rel activation, which is independent of IKKalpha and IKKbeta kinases and affects gene target(s) that are different from cytokine and TNFalpha-induced stress signaling. The results provide new insights into the role of Cn as a critical link between Ca2+ signaling and NFkappaB/Rel activation.
 ...
PMID:Mitochondria to nucleus stress signaling: a distinctive mechanism of NFkappaB/Rel activation through calcineurin-mediated inactivation of IkappaBbeta. 1273 17

The ryanodine receptor (RyR) is the major calcium (Ca(2+)) release channel in the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle and is required for excitation-contraction (EC) coupling. The 565 kDa RyR protein forms a tetrameric channel that is part of a macromolecular signaling complex that also includes four FK506 binding proteins (FKBPs). The RyR channel complex is localized on specialized regions of the SR, such that the large RyR cytoplasmic domain is closely opposed to the transverse tubule (T-tubule) of the plasma membrane. RyR channel complexes are organized in regular arrays such that neighboring RyRs are in physical contact with each other. We have shown that physical and functional association between RyR1 or RyR2 channels results in coordinated gating behavior termed coupled gating. Coupled gating requires FKBP12 or FKBP12.6 in the RyR1 or RyR2 macromolecular complexes, respectively. FKBPs are known to stabilize single RyR channel function. Coupled gating describes an additional role for FKBPs in the functional coordination of RyR channel complexes that allows clusters of channels to function as "Ca2+ release units" (CRU). In addition, the FKBP-RyR interaction is regulated by PKA phosphorylation. In failing hearts PKA hyperphosphorylation of RyR2 causes depletion of FKBP12.6 from the channel macromolecular complex and may contribute to contractile dysfunction by impairing EC coupling. As FKBPs are potent modulators of RyR channel function, the FKBP-RyR interaction is a focus for determining molecular mechanisms of coupled gating and presents an exciting pharmacologic target for restoration of RyR complex function in diseased states.
 ...
PMID:Immunophilins and coupled gating of ryanodine receptors. 1287 Nov 70

It is known that the two types of FK506-binding proteins FKBP12 and FKBP12.6 are tightly associated with the skeletal (RyR1) and cardiac ryanodine receptors (RyR2), respectively, and their interactions are important for channel functions of the RyR. In the case of cardiac muscle, three amino acid residues (Gln-31, Asn-32, and Phe-59) of FKBP12.6 could be essential for the selective binding to RyR2 (Xin, H. B., Rogers, K., Qi, Y., Kanematsu, T., and Fleischer, S. (1999) J. Biol. Chem. 274, 15315-15319). In this study to identify amino acid residues of FKBP12 that are important for the selective binding to RyR1, we mutated 9 amino acid residues of FKBP12 that differ from the counterparts of FKBP12.6 (Q3E, R18A, E31Q, D32N, M49R, R57A, W59F, H94A, and K105A), and we examined binding properties of these mutants to RyR1 by in vitro binding assay by using glutathione S-transferase-fused proteins of the mutants and Triton X-100-solubilized, FKBP12-depleted rabbit skeletal sarcoplasmic reticulum vesicles. Among the nine mutants tested, only Q3E and R18A lost their selective binding ability to RyR1. Furthermore, co-immunoprecipitation of RyR1 with 33 various mutants for the 9 positions produced by introducing different size, charge, and hydrophobicity revealed that an integration of the hydrogen bonds by the irreplaceable Gln-3 and the hydrophobic interactions by the residues Arg-18 and Met-49 could be a possible mechanism for the binding of FKBP12 to RyR1. Therefore, these results suggest that the N-terminal regions of FKBP12 (Gln-3 and Arg-18) and Met-49 are essential and unique for binding of FKBP12 to RyR1 in skeletal muscle.
 ...
PMID:N-terminal region of FKBP12 is essential for binding to the skeletal ryanodine receptor. 1503 87

The cellular and molecular processes underlying the regulation of ryanodine receptor (RyR) Ca(2+) release in smooth muscle cells (SMCs) are incompletely understood. Here we show that FKBP12.6 proteins are expressed in pulmonary artery (PA) smooth muscle and associated with type-2 RyRs (RyR2), but not RyR1, RyR3, or IP(3) receptors (IP(3)Rs) in PA sarcoplasmic reticulum. Application of FK506, which binds to FKBPs and dissociates these proteins from RyRs, induced an increase in [Ca(2+)](i) and Ca(2+)-activated Cl(-) and K(+) currents in freshly isolated PASMCs, whereas cyclosporin, an agent known to inhibit calcineurin but not to interact with FKBPs, failed to induce an increase in [Ca(2+)](i). FK506-induced [Ca(2+)](i) increase was completely blocked by the RyR antagonist ruthenium red and ryanodine, but not the IP(3)R antagonist heparin. Hypoxic Ca(2+) response and hypoxic vasoconstriction were significantly enhanced in FKBP12.6 knockout mouse PASMCs. FK506 or rapamycin pretreatment also enhanced hypoxic increase [Ca(2+)](i), but did not alter caffeine-induced Ca(2+) release (SR Ca(2+) content) in PASMCs. Norepinephrine-induced Ca(2+) release and force generation were also markedly enhanced in PASMCs from FKBP12.6 null mice. These findings suggest that FKBP12.6 plays an important role in hypoxia- and neurotransmitter-induced Ca(2+) and contractile responses by regulating the activity of RyRs in PASMCs.
 ...
PMID:Role of FKBP12.6 in hypoxia- and norepinephrine-induced Ca2+ release and contraction in pulmonary artery myocytes. 1503 51

The immunophilin FKBP12 binds the skeletal muscle Ca2+ release channel or ryanodine receptor (RyR1), but the functional consequences of this interaction are not known. In this study, we have generated skeletal muscle specific FKBP12-deficient mice to investigate the role of FKBP12 in skeletal muscle. Primary myotubes from these mice show no obvious change in either Ca2+ stores or resting Ca2+ levels but display decreased voltage-gated intracellular Ca2+ release and increased L-type Ca2+ currents. Consistent with the decreased voltage-gated Ca2+ release, maximal tetanic force production is decreased and the force frequency curves are shifted to the right in extensor digitorum longus (EDL) muscles of the mutant mice. In contrast, there is no decrease in maximal tetanic force production in the mutant diaphragm or soleus muscle. The force frequency curve is shifted to the left in the FKBP12-deficient diaphragm muscle compared with controls. No changes in myosin heavy chain (MHC) phenotype are observed in EDL or soleus muscle of the FKBP12-deficient mice, but diaphragm muscle displays an increased ratio of slow to fast MHC isoforms. Also, calcineurin levels are increased in the diaphragm of the mutant mice but not in the soleus or EDL. In summary, FKBP12 deficiency alters both orthograde and retrograde coupling between the L-type Ca2+ channel and RyR1 and the consequences of these changes depend on muscle type and activity. In highly used muscles such as the diaphragm, adaptation to the loss of FKBP12 occurs, possibly due to the increased Ca2+ influx.
 ...
PMID:Altered excitation-contraction coupling with skeletal muscle specific FKBP12 deficiency. 1528 41

Ryanodine receptors (RyRs) are the major sarcoplasmic reticulum calcium-release channels required for excitation-contraction coupling in skeletal and cardiac muscle. Mutations in RyRs have been linked to several human diseases. Mutations in the cardiac isoform of RyR2 are associated with catecholaminergic polymorphic ventricular arrhythmias (CPVT), and arrhythmogenic right ventricular dysplasia type 2 (ARVD2), whereas mutations in the skeletal muscle isoform (RyR1) are linked to malignant hyperthermia (MH) and central core disease (CCD). RyRs are modulated by several other proteins, including the FK506 binding proteins (FKBPs), FKBP12 and FKBP12.6. These immunophilins appear to stabilize a closed state of the channel and are important for cooperative interactions among the subunits of RyRs. This review discusses the regulation of RyRs by FKBPs and the possibility that defective modulation of RyR2 by FKBP12.6 could play a role in heart failure, CPVT, and ARVD2. Also discussed are the consequences of FKBP12 depletion to skeletal muscle and the possibility of FKBP12 involvement in certain forms of MH or CCD.
 ...
PMID:Regulation of ryanodine receptors by FK506 binding proteins. 1545 14

The ryanodine receptor-calcium release channel complex (RyR) plays a pivotal role in excitation-contraction coupling in skeletal and cardiac muscle. RyR channel activity is modulated by interaction with FK506-binding protein (FKBP), and disruption of the RyR-FKBP association has been implicated in cardiomyopathy, cardiac hypertrophy, and heart failure. Evidence for an interaction between RyR and FKBP is well documented, both in skeletal muscle (RyR1-FKBP12) and in cardiac muscle (RyR2-FKBP12.6), however definition of the FKBP-binding site remains elusive. Early reports proposed interaction of a short RyR central domain with FKBP12/12.6, however this site has been questioned, and recently an alternative FKBP12.6 interaction site has been identified within the N-terminal half of RyR2. In this study, we report evidence for the human RyR2 C-terminal domain as a novel FKBP12.6-binding site. Using competition binding assays, we find that short C-terminal RyR2 fragments can displace bound FKBP12.6 from the native RyR2, although they are unable to exclusively support interaction with FKBP12.6. However, expression of a large RyR2 C-terminal construct in mammalian cells encompassing the pore-forming transmembrane domains exhibits rapamycin-sensitive binding specifically to FKBP12.6 but not to FKBP12. We also obtained some evidence for involvement of the RyR2 N-terminal, but not the central domain, in FKBP12.6 interaction. Our studies suggest that a novel interaction site for FKBP12.6 may be present at the RyR2 C terminus, proximal to the channel pore, a sterically appropriate location that would enable this protein to play a central role in the modulation of this critical ion channel.
 ...
PMID:Interaction of FKBP12.6 with the cardiac ryanodine receptor C-terminal domain. 1559 Oct 45

Depletion of mitochondrial DNA (mtDNA) or treatment with mitochondrial poison CCCP initiates mitochondrial stress signaling, which operates through altered Ca2+ homeostasis. In C2C12 rhabdomyoblasts and A549 human lung carcinoma cells mitochondrial stress signaling activates calcineurin and a number of Ca2+ responsive factors including ATF, NFAT, CEBP/delta and CREB. Additionally, PKC and MAP kinase are also activated. A number of nuclear gene targets including those involved in Ca2+ storage/release (RyR1, calreticulin, calsequestrin), glucose metabolism (hexokinase, pyruvate kinase, Glut4), oncogenesis (TGFbeta1, cathepsin L, IGFR1, melanoma antigen) and apoptosis (Bcl-2, Bid, Bad, p53) are upregulated. Mitochondrial stress in both C2C12 myoblasts and A549 cells induced morphological changes and invasive phenotypes. These cells also showed markedly increased resistance to etoposide-induced apoptosis that is a hallmark of highly invasive tumors. Our results describe a new mechanism of altered nuclear gene expression and phenotypic changes triggered by mitochondrial dysfunction and mtDNA damage.
 ...
PMID:Mitochondria-to-nucleus stress signaling in mammalian cells: nature of nuclear gene targets, transcription regulation, and induced resistance to apoptosis. 1597 49


<< Previous 1 2 3 4 5 Next >>