scholarly journals Cooperative and acute inhibition by multiple C-terminal motifs of L-type Ca2+ channels

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Nan Liu ◽  
Yaxiong Yang ◽  
Lin Ge ◽  
Min Liu ◽  
Henry M Colecraft ◽  
...  
Keyword(s):  
Computational Modeling ◽  
Therapeutic Potential ◽  
Regulatory Domain ◽  
New Paradigm ◽  
C Terminus ◽  
Dependent Inactivation ◽  
End Stage ◽  
Lower Limits ◽  
Full Activation ◽  
Ca2 Channels

Inhibitions and antagonists of L-type Ca2+ channels are important to both research and therapeutics. Here, we report C-terminus mediated inhibition (CMI) for CaV1.3 that multiple motifs coordinate to tune down Ca2+ current and Ca2+ influx toward the lower limits determined by end-stage CDI (Ca2+-dependent inactivation). Among IQV (preIQ3-IQ domain), PCRD and DCRD (proximal or distal C-terminal regulatory domain), spatial closeness of any two modules, e.g., by constitutive fusion, facilitates the trio to form the complex, compete against calmodulin, and alter the gating. Acute CMI by rapamycin-inducible heterodimerization helps reconcile the concurrent activation/inactivation attenuations to ensure Ca2+ influx is reduced, in that Ca2+ current activated by depolarization is potently (~65%) inhibited at the peak (full activation), but not later on (end-stage inactivation, ~300 ms). Meanwhile, CMI provides a new paradigm to develop CaV1 inhibitors, the therapeutic potential of which is implied by computational modeling of CaV1.3 dysregulations related to Parkinson’s disease.

scholarly journals The STIM1 CTID domain determines access of SARAF to SOAR to regulate Orai1 channel function

2013 ◽  
Vol 202 (1) ◽  
pp. 71-79 ◽  
Author(s):  
Archana Jha ◽  
Malini Ahuja ◽  
József Maléth ◽  
Claudia M. Moreno ◽  
Joseph P. Yuan ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Cell Damage ◽  
Cell Functions ◽  
Dependent Inactivation ◽  
Dependent Cell ◽  
Inhibitory Domain ◽  
Molecular Components ◽  
Full Activation ◽  
Ca2 Channels

Ca2+ influx by store-operated Ca2+ channels (SOCs) mediates all Ca2+-dependent cell functions, but excess Ca2+ influx is highly toxic. The molecular components of SOC are the pore-forming Orai1 channel and the endoplasmic reticulum Ca2+ sensor STIM1. Slow Ca2+-dependent inactivation (SCDI) of Orai1 guards against cell damage, but its molecular mechanism is unknown. Here, we used homology modeling to identify a conserved STIM1(448–530) C-terminal inhibitory domain (CTID), whose deletion resulted in spontaneous clustering of STIM1 and full activation of Orai1 in the absence of store depletion. CTID regulated SCDI by determining access to and interaction of the STIM1 inhibitor SARAF with STIM1 Orai1 activation region (SOAR), the STIM1 domain that activates Orai1. CTID had two lobes, STIM1(448–490) and STIM1(490–530), with distinct roles in mediating access of SARAF to SOAR. The STIM1(448–490) lobe restricted, whereas the STIM1(490–530) lobe directed, SARAF to SOAR. The two lobes cooperated to determine the features of SCDI. These findings highlight the central role of STIM1 in SCDI and provide a molecular mechanism for SCDI of Orai1.

scholarly journals A CACNA1A variant associated with trigeminal neuralgia alters the gating of Cav2.1 channels

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Eder Gambeta ◽  
Maria A. Gandini ◽  
Ivana A. Souza ◽  
Laurent Ferron ◽  
Gerald W. Zamponi
Keyword(s):  
Trigeminal Neuralgia ◽  
Missense Mutation ◽  
Neurotransmitter Release ◽  
Trigeminal System ◽  
Wild Type ◽  
Calcium Dependent ◽  
Whole Cell Patch Clamp ◽  
C Terminus ◽  
Dependent Inactivation

AbstractA novel missense mutation in the CACNA1A gene that encodes the pore forming α1 subunit of the CaV2.1 voltage-gated calcium channel was identified in a patient with trigeminal neuralgia. This mutation leads to a substitution of proline 2455 by histidine (P2455H) in the distal C-terminus region of the channel. Due to the well characterized role of this channel in neurotransmitter release, our aim was to characterize the biophysical properties of the P2455H variant in heterologously expressed CaV2.1 channels. Whole-cell patch clamp recordings of wild type and mutant CaV2.1 channels expressed in tsA-201 cells reveal that the mutation mediates a depolarizing shift in the voltage-dependence of activation and inactivation. Moreover, the P2455H mutant strongly reduced calcium-dependent inactivation of the channel that is consistent with an overall gain of function. Hence, the P2455H CaV2.1 missense mutation alters the gating properties of the channel, suggesting that associated changes in CaV2.1-dependent synaptic communication in the trigeminal system may contribute to the development of trigeminal neuralgia.

scholarly journals Sir3p Domains Involved in the Initiation of Telomeric Silencing in Saccharomyces cerevisiae

Genetics ◽  
1998 ◽  
Vol 150 (3) ◽  
pp. 977-986 ◽  
Author(s):  
Yangsuk Park ◽  
John Hanish ◽  
Arthur J Lustig
Keyword(s):  
Amino Acids ◽  
Active Site ◽  
Fusion Proteins ◽  
Initiation Site ◽  
Negative Control ◽  
Model System ◽  
Mutant Protein ◽  
Regulatory Domain ◽  
C Terminus ◽  
Necessary And Sufficient

Abstract Previous studies from our laboratory have demonstrated that tethering of Sir3p at the subtelomeric/telomeric junction restores silencing in strains containing Rap1-17p, a mutant protein unable to recruit Sir3p. This tethered silencing assay serves as a model system for the early events that follow recruitment of silencing factors, a process we term initiation. A series of LexA fusion proteins in-frame with various Sir3p fragments were constructed and tested for their ability to support tethered silencing. Interestingly, a region comprising only the C-terminal 144 amino acids, termed the C-terminal domain (CTD), is both necessary and sufficient for restoration of silencing. Curiously, the LexA-Sir3N205 mutant protein overcomes the requirement for the CTD, possibly by unmasking a cryptic initiation site. A second domain spanning amino acids 481-835, termed the nonessential for initiation domain (NID), is dispensable for the Sir3p function in initiation, but is required for the recruitment of the Sir4p C terminus. In addition, in the absence of the N-terminal 481 amino acids, the NID negatively influences CTD activity. This suggests the presence of a third region, consisting of the N-terminal half (1-481) of Sir3p, termed the positive regulatory domain (PRD), which is required to initiate silencing in the presence of the NID. These data suggest that the CTD “active” site is under both positive and negative control mediated by multiple Sir3p domains.

scholarly journals Differential Interactions of the C terminus and the Cytoplasmic I-II Loop of Neuronal Ca2+Channels with G-protein α and βγ Subunits

1998 ◽  
Vol 273 (28) ◽  
pp. 17595-17603 ◽  
Author(s):  
Taiji Furukawa ◽  
Reiko Miura ◽  
Yasuo Mori ◽  
Mark Strobeck ◽  
Kazuyuki Suzuki ◽  
...  
Keyword(s):  
G Protein ◽  
C Terminus ◽  
Ca2 Channels

Wogonin preferentially kills malignant lymphocytes and suppresses T-cell tumor growth by inducing PLCγ1- and Ca2+-dependent apoptosis

Blood ◽  
2008 ◽  
Vol 111 (4) ◽  
pp. 2354-2363 ◽  
Author(s):  
Sven Baumann ◽  
Stefanie C. Fas ◽  
Marco Giaisi ◽  
Wolfgang W. Müller ◽  
Anette Merling ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Chinese Medicine ◽  
Traditional Chinese Medicine ◽  
Therapeutic Potential ◽  
Human T Cell ◽  
Voltage Dependent ◽  
Ca2 Channels ◽  
Malignant T Cells

Herbs have successfully been used in traditional Chinese medicine for centuries. However, their curative mechanisms remain largely unknown. In this study, we show that Wogonin, derived from the traditional Chinese medicine Huang-Qin (Scutellaria baicalensis Georgi), induces apoptosis in malignant T cells in vitro and suppresses growth of human T-cell leukemia xenografts in vivo. Importantly, Wogonin shows almost no toxicity on T lymphocytes from healthy donors. Wogonin induces prolonged activation of PLCγ1 via H2O2 signaling in malignant T cells, which leads to sustained elevation of cytosolic Ca2+ in malignant but not normal T cells. Subsequently, a Ca2+ overload leads to disruption of the mitochondrial membrane. The selective effect of Wogonin is due to its differential regulation of the redox status of malignant versus normal T cells. In addition, we show that the L-type voltage-dependent Ca2+ channels are involved in the intracellular Ca2+ mobilization in T cells. Furthermore, we show that malignant T cells possess elevated amounts of voltage-dependent Ca2+ channels compared with normal T cells, which further enhance the cytotoxicity of Wogonin for malignant T cells. Taken together, our data show a therapeutic potential of Wogonin for the treatment of hematologic malignancies.

scholarly journals A Complex of RIM2alpha and RIM-Binding Protein 2 Stabilizes Slow Voltage-Dependent Inactivation of Cochlear Inner Hair Cell Cav1.3 L-Type Ca2+ Channels

2018 ◽  
Vol 114 (3) ◽  
pp. 637a-638a
Author(s):  
Nadine J. Ortner ◽  
Alexandra Pinggera ◽  
Anita Siller ◽  
Nadja Hofer ◽  
Niels Brandt ◽  
...  
Keyword(s):  
Hair Cell ◽  
Binding Protein ◽  
Inner Hair Cell ◽  
Dependent Inactivation ◽  
Voltage Dependent ◽  
Ca2 Channels

scholarly journals A bilobal model of Ca2+-dependent inactivation to probe the physiology of L-type Ca2+ channels

2018 ◽  
Vol 150 (12) ◽  
pp. 1688-1701 ◽  
Author(s):  
Worawan B. Limpitikul ◽  
Joseph L. Greenstein ◽  
David T. Yue ◽  
Ivy E. Dick ◽  
Raimond L. Winslow
Keyword(s):  
Building Blocks ◽  
Downstream Signaling ◽  
Critical Elements ◽  
Cardiac Electrical Activity ◽  
Dependent Inactivation ◽  
Life Threatening ◽  
Detailed Kinetic Model ◽  
Ca2 Channels ◽  
Normal Cardiac Function ◽  
Experimental Challenge

L-type calcium channels (LTCCs) are critical elements of normal cardiac function, playing a major role in orchestrating cardiac electrical activity and initiating downstream signaling processes. LTCCs thus use feedback mechanisms to precisely control calcium (Ca2+) entry into cells. Of these, Ca2+-dependent inactivation (CDI) is significant because it shapes cardiac action potential duration and is essential for normal cardiac rhythm. This important form of regulation is mediated by a resident Ca2+ sensor, calmodulin (CaM), which is comprised of two lobes that are each capable of responding to spatially distinct Ca2+ sources. Disruption of CaM-mediated CDI leads to severe forms of long-QT syndrome (LQTS) and life-threatening arrhythmias. Thus, a model capable of capturing the nuances of CaM-mediated CDI would facilitate increased understanding of cardiac (patho)physiology. However, one critical barrier to achieving a detailed kinetic model of CDI has been the lack of quantitative data characterizing CDI as a function of Ca2+. This data deficit stems from the experimental challenge of uncoupling the effect of channel gating on Ca2+ entry. To overcome this obstacle, we use photo-uncaging of Ca2+ to deliver a measurable Ca2+ input to CaM/LTCCs, while simultaneously recording CDI. Moreover, we use engineered CaMs with Ca2+ binding restricted to a single lobe, to isolate the kinetic response of each lobe. These high-resolution measurements enable us to build mathematical models for each lobe of CaM, which we use as building blocks for a full-scale bilobal model of CDI. Finally, we use this model to probe the pathogenesis of LQTS associated with mutations in CaM (calmodulinopathies). Each of these models accurately recapitulates the kinetics and steady-state properties of CDI in both physiological and pathological states, thus offering powerful new insights into the mechanistic alterations underlying cardiac arrhythmias.

Abstract 15: Limiting GRK2 in the Ischemic Heart can Promote Cardiac Regeneration

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Maria Cecilia Scimia ◽  
Lin Zuo ◽  
Kate E Sydnes ◽  
Daniel A Zuppo ◽  
Erhe Gao ◽  
...  
Keyword(s):  
Therapeutic Potential ◽  
Cardiac Injury ◽  
Cardiac Regeneration ◽  
Cardiac Repair ◽  
Functional Improvement ◽  
Coronary Artery Ligation ◽  
Therapeutic Effects ◽  
Artery Ligation ◽  
C Terminus ◽  
Independent Effects

The detrimental role of G protein-coupled receptor (GPCR) kinase (GRK2) following cardiac injury/stress has been documented over the last two decades. Importantly, our lab has shown that inhibition or deletion of GRK2 in cardiomyocytes can prevent and also rescue heart failure (HF) phenotypes. Its role in GPCR desensitization including regulation of β-adrenergic receptors (βARs) during HF development has been well characterized. However, recently our lab and others have found that GRK2 can have novel GPCR-independent effects in the heart that appear to contribute to its pathological effects and thus, inhibition of these actions of GRK2 may contribute to therapeutic effects seen. In this study we explored whether the cardiac repair observed with lower myocardial GRK2 might involve regenerative processes. In cardiac-specific GRK2 knockout (KO) mice and also transgenic mice with cardiac-targeted expression of the βARKct, a peptide inhibitor of GRK2 activation via Gβγ sequestration, we induced HF via coronary artery ligation and subsequent myocardial infarction (MI) and measured aspects of cardiac repair including potential regeneration indices. Post-MI mice (GRK2 KO, βARKct mice and wild-type and non-transgenic control mice) were treated with 5-ethynyl-2’-deoxyuridine (EdU) or Bromodeoxyuridine (BrDU) to examine indices of DNA proliferation in myocytes as well as Ki67 staining. We also quantitated c-kit+ cells and myocytes in the post-MI hearts to compare how either loss of GRK2 expression or inhibition via its C-terminus altered potential regeneration mechanisms compared to control mice with endogenous GRK2 levels and activity. We found significantly more BrDU positive myocytes in post-MI hearts with lower GRK2 and this correlated with increased myocytes that were also cKit+. Thus, it appears that the myocardial functional improvement seen in the post-MI heart with targeted lowering of GRK2 involves, to at least a certain extent, regenerative mechanisms. This adds novel insight into the therapeutic potential of GRK2 inhibition for HF.

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