The random-coil ‘C’ fragment of the dihydropyridine receptor II-III loop can activate or inhibit native skeletal ryanodine receptors

Haarmann, Claudia; Green, Daniel; Casarotto, Marco G.; Laver, Derek R.; Dulhunty, Angela F.

doi:10.1042/bj20021763

Cited by 43 publications

(49 citation statements)

References 41 publications

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“…However, their predictions need to be tested with more experimental structural methods. The random coil structure of this region in the skeletal DHPR II-III loop was recently confirmed by NMR and CD (36); however, NMR analysis of the corresponding cardiac region is still elusive. If our structure predictions are correct, it is likely that not only the presence or absence of individual residues but also the consequences of such substitutions on the secondary structure of the adjacent negatively charged cluster determine the tissue-specific mode of interaction between the DHPR and the RyR1.…”

Section: Discussionmentioning

confidence: 99%

Structural Requirements of the Dihydropyridine Receptor α1S II-III Loop for Skeletal-type Excitation-Contraction Coupling

Kugler

Weiß

Flucher

et al. 2004

Journal of Biological Chemistry

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Residues Leu720 -Leu 764 within the II-III loop of the skeletal muscle dihydropyridine receptor (DHPR) ␣ 1S subunit represent a critical domain for the orthograde excitation-contraction coupling as well as for retrograde DHPR L-current-enhancing coupling with the ryanodine receptor (RyR1). To better understand the molecular mechanism underlying this bidirectional DHPRRyR1 signaling interaction, we analyzed the critical domain to the single amino acid level. To this end, constructs based on the highly dissimilar housefly DHPR II-III loop in an otherwise skeletal DHPR as an interaction-inert sequence background were expressed in dys- of ␣ 1S ) corresponds with significantly reduced Ca 2؉ transients. Conversely, a predicted random coil structure (skeletal sequence-type) seems to be prerequisite for the restoration of skeletal-type excitation-contraction coupling. Thus, not only the primary but also the secondary structure of the critical domain is an essential determinant of the tissue-specific mode of EC coupling. Excitation-contraction (EC)1 coupling in skeletal muscle is understood as a protein-protein or "mechanical" interaction of two distinct Ca 2ϩ channels, the voltage-gated L-type Ca 2ϩ channel or dihydropyridine receptor (DHPR) and the Ca 2ϩ release channel or ryanodine receptor (RyR1) in the sarcoplasmic reticulum (1, 2; reviewed in Refs. 3 and 4). Therefore, skeletal-type EC coupling is independent from the influx of extracellular Ca 2ϩ (5-7), in contrast to cardiac EC coupling where Ca 2ϩ influx is required to trigger the release of intracellular Ca 2ϩ from the sarcoplasmic reticulum stores (8), which in turn activates contraction. In skeletal muscle EC coupling the voltage-sensing DHPR undergoes voltage-driven conformational changes that are allosterically communicated to RyR1 via the cytoplasmic loop connecting the homologous repeats II and III of the pore-forming DHPR ␣ 1S subunit (2, 9). The II-III loop is not only important for transmitting this orthograde EC coupling signal to the RyR1, it also receives a retrograde, current-enhancing signal from the RyR1 to the DHPR (10, 11). Beside unequivocally strong indications for an essential role of the II-III loop for this bidirectional coupling mechanism, accumulating evidence suggests an additional influence of other regions of the DHPR ␣ 1S subunit and/or of the accessory ␤ subunit (12, 13).Nevertheless, one sequence portion of the skeletal DHPR ␣ 1S II-III loop (Leu 720 -Leu 764 ) was previously shown to be essential for bidirectional coupling (11,14,15). These 45 residues inserted into the corresponding regions of ␣ 1 subunit chimeras that contain II-III loops incapable of direct skeletal-type (Ca 2ϩ -independent) coupling, like the cardiac II-III loop (11,14) or the highly heterologous II-III loop of the housefly (Musca domestica) DHPR (15), fully restored orthograde and retrograde signaling when expressed in dysgenic (␣ 1S -null) myotubes. Based on the observation that bidirectional coupling was unaffected by drastic alterations of the sequence sur...

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Section: Discussionmentioning

confidence: 99%

Structural Requirements of the Dihydropyridine Receptor α1S II-III Loop for Skeletal-type Excitation-Contraction Coupling

Kugler

Weiß

Flucher

et al. 2004

Journal of Biological Chemistry

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“…The strongly α-helical basic 'A' region peptide [21] also activates RyR1 with high affinity [10][11][12]20,22]. These functional interactions possibly reflect binding reactions that contribute to the protein-protein interactions in skeletal muscle [18,20]. The fact that the A peptides also interact with RyR2 provides evidence for potential DHPR-RyR interactions in the heart [13].…”

Section: Introductionmentioning

confidence: 88%

“…• C. Peptide C S has been shown previously to have a random coil structure at room temperature [18]. The lack of crosspeaks in the NOESY spectra for C C ( Figure 8B) suggest that the cardiac C peptide is also random coil at 25…”

Section: Does the Ii-iii Loop Bind To Ryr2 Via Its A Or C Region?mentioning

confidence: 94%

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The recombinant dihydropyridine receptor II–III loop and partly structured ‘C’ region peptides modify cardiac ryanodine receptor activity

Dulhunty

Karunasekara

Curtis

et al. 2005

Biochemical Journal

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A physical association between the II-III loop of the DHPR (dihydropryidine receptor) and the RyR (ryanodine receptor) is essential for excitation-contraction coupling in skeletal, but not cardiac, muscle. However, peptides corresponding to a part of the II-III loop interact with the cardiac RyR2 suggesting the possibility of a physical coupling between the proteins. Whether the full II-III loop and its functionally important 'C' region (cardiac DHPR residues 855-891 or skeletal 724-760) interact with cardiac RyR2 is not known and is examined in the present study. Both the cardiac DHPR II-III loop (CDCL) and cardiac peptide (C C ) activated RyR2 channels at concentrations >10 nM. The skeletal DHPR II-III loop (SDCL) activated channels at 100 nM and weakly inhibited at 1 µM. In contrast, skeletal peptide (C S ) inhibited channels at all concentrations when added alone, or was ineffective if added in the presence of C C . Ca 2+ -induced Ca 2+ release from cardiac sarcoplasmic reticulum was enhanced by CDCL, SDCL and the C peptides. The results indicate that the interaction between the II-III loop and RyR2 depends critically on the 'A' region (skeletal DHPR residues 671-690 or cardiac 793-812) and also involves the C region. Structure analysis indicated that (i) both C S and C C are random coil at room temperature, but, at 5• C, have partial helical regions in their N-terminal and central parts, and (ii) secondary-structure profiles for CDCL and SDCL are similar. The data provide novel evidence that the DHPR II-III loop and its C region interact with cardiac RyR2, and that the ability to interact is not isoform-specific.

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“…In particular, 1) the concentration of the Tpx-1 Crisp domain required for inhibition of RyR2 was half that required for the activation of RyR1 and; 2) RyR2 inhibition could not be reversed at higher Tpx-1 Crisp domain concentrations following perfusion. The 1000 -10,000-fold dilution of protein following perfusion (66), which would have left 5-50 nM of the Tpx-1 Crisp domain, was sufficient to maintain inhibition. A greater affinity of the Tpx-1 Crisp domain for the inhibition site on RyR2 is in contrast with that reported for helothermine (28), which had a greater affinity for the activation site on RyR1.…”

Section: The Tpx-1 Crisp Domain Is a Conserved Structural Element Dismentioning

confidence: 99%

The Cysteine-rich Secretory Protein Domain of Tpx-1 Is Related to Ion Channel Toxins and Regulates Ryanodine Receptor Ca2+ Signaling

Gibbs

Scanlon

Swarbrick

et al. 2006

Journal of Biological Chemistry

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126

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The cysteine-rich secretory proteins (Crisp) are predominantly found in the mammalian male reproductive tract as well as in the venom of reptiles. Crisps are two domain proteins with a structurally similar yet evolutionary diverse N-terminal domain and a characteristic cysteine-rich C-terminal domain, which we refer to as the Crisp domain. We presented the NMR solution structure of the Crisp domain of mouse Tpx-1, and we showed that it contains two subdomains, one of which has a similar fold to the ion channel regulators BgK and ShK. Furthermore, we have demonstrated for the first time that the ion channel regulatory activity of Crisp proteins is attributed to the Crisp domain. Specifically, the Tpx-1 Crisp domain inhibited cardiac ryanodine receptor (RyR) 2 with an IC 50 between 0.5 and 1.0 M and activated the skeletal RyR1 with an AC 50 between 1 and 10 M when added to the cytoplasmic domain of the receptor. This activity was nonvoltage-dependent and weakly voltage-dependent, respectively. Furthermore, the Tpx-1 Crisp domain activated both RyR forms at negative bilayer potentials and showed no effect at positive bilayer potentials when added to the luminal domain of the receptor. These data show that the Tpx-1 Crisp domain on its own can regulate ion channel activity and provide compelling evidence for a role for Tpx-1 in the regulation of Ca 2؉ fluxes observed during sperm capacitation.Tpx-1 (testis specific protein-1) was originally identified in the mouse (1) and later found in the male reproductive tract of the human, guinea pig, rat, and horse (2-5). Tpx-1 is a member of the cysteine-rich secretory proteins (Crisp) 2 that are in turn a subgroup of the CAP protein superfamily (abbreviated from Crisp, Antigen 5, and Pr-1 (6)). The CAP proteins each contain a structurally related and unique domain, the CAP domain (7)(8)(9), that at present has no clearly defined biological function, although their spatial and temporal expression suggests a function related to the regulation of the innate immune system (10, 11) and male reproductive function. The Crisp proteins have a characteristic C-terminal sequence containing 10 absolutely conserved cysteines. The Crisp domain is unique and is only observed in association with the CAP domain. Previously, there has been no biological activity attributed specifically to this domain.In mammals, there are at least four Crisp proteins, Crisp-1, Tpx-1 (or Crisp-2), Crisp-3, and Crisp-4. Crisp-1 proteins are expressed predominantly in the epididymides where they coat the surface of sperm during epididymal maturation (12) and have been implicated in sperm oocyte binding and the regulation of capacitation (13-17). Tpx-1 is expressed only in the testis and localized to specific regions in the spermatozoa, notably the acrosome of the head, the outer dense fibers, and longitudinal columns of the fibrous sheath in the sperm tail and the connecting piece of the neck (3, 18). Transfection experiments have also suggested that Tpx-1 is involved in adhesion between germ cells and Sertoli...

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The random-coil ‘C’ fragment of the dihydropyridine receptor II-III loop can activate or inhibit native skeletal ryanodine receptors

Cited by 43 publications

References 41 publications

Structural Requirements of the Dihydropyridine Receptor α1S II-III Loop for Skeletal-type Excitation-Contraction Coupling

Structural Requirements of the Dihydropyridine Receptor α1S II-III Loop for Skeletal-type Excitation-Contraction Coupling

The recombinant dihydropyridine receptor II–III loop and partly structured ‘C’ region peptides modify cardiac ryanodine receptor activity

The Cysteine-rich Secretory Protein Domain of Tpx-1 Is Related to Ion Channel Toxins and Regulates Ryanodine Receptor Ca2+ Signaling

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