Cell calcium最新文献

The non-selective cation channel TRPC1 is highly expressed in the brain. Recent research shows that neuronal TRPC1 forms heteromeric complexes with TRPC4 and TRPC5, with a small portion existing as homotetramers, primarily in the ER. Given that most studies have focused on the role of heteromeric TRPC1/4/5 complexes, it is crucial to investigate the specific role of homomeric TRPC1 in maintaining brain homeostasis. This review highlights recent findings on TRPC1 in the brain, with a focus on the hippocampus, and compiles the latest data on modulators and their binding sites within the TRPC1/4/5 subfamily to stimulate new research on more selective TRPC1 ligands.

Transient receptor potential canonical 3 (TRPC3) is a calcium-permeable, non-selective cation channel known to be regulated by components of the phospholipase C (PLC)-mediated signaling pathway, such as Ca²⁺, diacylglycerol (DAG) and phosphatidylinositol 4,5-biphosphate (PI(4,5)P₂). However, the molecular gating mechanism by these regulators is not yet fully understood, especially its regulation by PI(4,5)P₂, despite the importance of this channel in cardiovascular pathophysiology. Recently, Clarke et al. (2024) have reported that PI(4,5)P₂ is a positive modulator for TRPC3 using molecular dynamics simulations and patch-clamp techniques. They have demonstrated a multistep gating mechanism of TRPC3 with the binding of PI(4,5)P₂ to the lipid binding site located at the pre-S1/S1 nexus, and the propagation of PI(4,5)P₂ sensing to the pore domain via a salt bridge between the TRP helix and the S4–S5 linker.

Urethral smooth muscle cells (USMC) contract to occlude the internal urethral sphincter during bladder filling. Interstitial cells also exist in urethral smooth muscles and are hypothesized to influence USMC behaviours and neural responses. These cells are similar to Kit⁺ interstitial cells of Cajal (ICC), which are gastrointestinal pacemakers and neuroeffectors. Isolated urethral ICC-like cells (ICC-LC) exhibit spontaneous intracellular Ca²⁺ signalling behaviours that suggest these cells may serve as pacemakers or neuromodulators similar to ICC in the gut, although observation and direct stimulation of ICC-LC within intact urethral tissues is lacking. We used mice with cell-specific expression of the Ca²⁺ indicator, GCaMP6f, driven off the endogenous promoter for Kit (Kit-GCaMP6f mice) to identify ICC-LC in situ within urethra muscles and to characterize spontaneous and nerve-evoked Ca²⁺ signalling. ICC-LC generated Ca²⁺ waves spontaneously that propagated on average 40.1 ± 0.7 μm, with varying amplitudes, durations, and spatial spread. These events originated from multiple firing sites in cells and the activity between sites was not coordinated. ICC-LC in urethra formed clusters but not interconnected networks. No evidence for entrainment of Ca²⁺ signalling between ICC-LC was obtained. Ca²⁺ events in ICC-LC were unaffected by nifedipine but were abolished by cyclopiazonic acid and decreased by an antagonist of Orai Ca²⁺ channels (GSK-7975A). Phenylephrine increased Ca²⁺ event frequency but a nitric oxide donor (DEA-NONOate) had no effect. Electrical field stimulation (EFS, 10 Hz) of intrinsic nerves, which evoked contractions of urethral rings and increased Ca²⁺ event firing in USMC, failed to evoke responses in ICC-LC. Our data suggest that urethral ICC-LC are spontaneously active but are not regulated by autonomic neurons.

Aberrant Ca²⁺ signaling is an early hallmark of multiple neurodegenerative syndromes including Alzheimer's and Parkinson's disease (AD and PD) as well as classes of rare genetic disorders such as Spinocebellar Ataxias. Therapeutic strategies that target aberrant Ca²⁺ signals whilst allowing normal neuronal Ca²⁺ signals have been a challenge. In a recent study Princen et al., performed a screen in the tauP301L cell model of AD for drugs that could specifically ameliorate the excess Ca²⁺ entry observed. They identified a class of compounds referred to as ReS19-T that interact with Septins, previously identified as regulators of the Store-operated Ca²⁺ entry channel Orai. Drug treatment of the cellular model, a mouse model and human iPSC derived neurons alleviate cellular and systemic deficits associated with tauP301L. Comparison of Septin filament architecture in disease conditions with and without the drug treatment indicate that excess Ca²⁺ entry is a consequence of abnormal Septin filament architecture resulting in aberrant ER-PM contacts. The importance of membrane contacts for maintaining precise cellular signaling has been recognized previously. However, the molecular mechanism by which Septin filaments organize the ER-PM junctions to regulate Ca²⁺ entry through Orai remains to be fully understood.

As the uncontrolled entry of calcium ions (Ca²⁺) through plasmalemmal calcium channels is a cell death trigger, the conjecture is here raised that mitigating such an excess of Ca²⁺ entry should rescue from death the vulnerable neurons in neurodegenerative diseases (NDDs). However, this supposition has failed in some clinical trials (CTs). Thus, a recent CT tested whether isradipine, a blocker of the Cav1 subtype of voltage-operated calcium channels (VOCCs), exerted a benefit in patients with Parkinson's disease (PD); however, outcomes were negative. This is one more of the hundreds of CTs done under the principle of one-drug-one-target, that have failed in Alzheimer's disease (AD) and other NDDs during the last three decades. As there are myriad calcium channels to let Ca²⁺ ions gain the cell cytosol, it seems reasonable to predict that blockade of Ca²⁺ entry through a single channel may not be capable of preventing the Ca²⁺ flood of cells by the uncontrolled Ca²⁺ entry. Furthermore, as Ca²⁺ signaling is involved in the regulation of myriad functions in different cell types, it seems also reasonable to guess that a therapy should be more efficient by targeting different cells with various drugs. Here, we propose to mitigate Ca²⁺ entry by the simultaneous partial blockade of three quite different subtypes of plasmalemmal calcium channels that is, the Cav1 subtype of VOCCs, the Orai1 store-operated calcium channel (SOCC), and the purinergic P2X7 calcium channel. All three channels are expressed in both microglia and neurons. Thus, by targeting the three channels with a combination of three drug blockers we expect favorable changes in some of the pathogenic features of NDDs, namely (i) to mitigate Ca²⁺ entry into microglia; (ii) to decrease the Ca²⁺-dependent microglia activation; (iii) to decrease the sustained neuroinflammation; (iv) to decrease the uncontrolled Ca²⁺ entry into neurons; (v) to rescue vulnerable neurons from death; and (vi) to delay disease progression. In this review we discuss the arguments underlying our triad hypothesis in the sense that the combination of three repositioned medicines targeting Cav1, Orai1, and P2X7 calcium channels could boost neuroprotection and delay the progression of AD and other NDDs.

In order to understand protein function, the field of structural biology makes extensive use of cryogenic electron microscopy (cryo-EM), a technique that enables structure determination at atomic resolution following embedding of protein particles in vitreous ice. Considering the profound effects of temperature on macromolecule function, an important—but often neglected-question is how the frozen particles relate to the actual protein conformations at physiological temperatures. In a recent study, Hu et al. compare structures of the cation channel TRPM4 “frozen” at 4 °C versus 37 °C, revealing how temperature critically affects the binding of activating Ca²⁺ ions and other channel modulators.

Two recent papers have highlighted that STIM1, a key component of Store-operated Ca2+-entry, is able to translocate to the nucleus and participate in nuclear Ca²⁺-handling and in DNA repair. These finding opens new avenues on the role that this Ca²⁺-sensing protein may have in health and disease.

Anoctamin 1 (ANO1/TMEM16A) encodes a Ca²⁺-activated Cl^- channel. Among ANO1′s many physiological functions, it plays a significant role in mediating nociception and itch. ANO1 is activated by intracellular Ca²⁺ and depolarization. Additionally, ANO1 is activated by heat above 44 °C, suggesting heat as another activation stimulus. ANO1 is highly expressed in nociceptors, indicating a role in nociception. Conditional Ano1 ablation in dorsal root ganglion (DRG) neurons results in a reduction in acute thermal pain, as well as thermal and mechanical allodynia or hyperalgesia evoked by inflammation or nerve injury. Pharmacological interventions also lead to a reduction in nocifensive behaviors. ANO1 is functionally linked to the bradykinin receptor and TRPV1. Bradykinin stimulates ANO1 via IP3-mediated Ca²⁺ release from intracellular stores, whereas TRPV1 stimulates ANO1 via a combination of Ca²⁺ influx and release. Nerve injury causes upregulation of ANO1 expression in DRG neurons, which is blocked by ANO1 antagonists. Due to its role in nociception, strong and specific ANO1 antagonists have been developed. ANO1 is also expressed in pruritoceptors, mediating Mas-related G protein-coupled receptors (Mrgprs)-dependent itch. The activation of ANO1 leads to chloride efflux and depolarization due to high intracellular chloride concentrations, causing pain and itch. Thus, ANO1 could be a potential target for the development of new drugs treating pain and itch.

Aims

Previous studies have identified RyR2 W4645R mutation, located in the caffeine-binding site, to associate with CPVT1 pathology. Caffeine binding to its site is thought to displace the carboxyl-terminal domain to Ca²⁺-binding, allowing the tryptophan residue (W4645) to regulate Ca²⁺ sensitivity of RyR2. To gain insights into regulation of RyR2 Ca²⁺-binding and its interaction with caffeine-binding site, we introduced W4645R-RyR2 point mutation via CRISPR/Cas9 gene-editing in human induced pluripotent stem cell-derived cardiomyocytes (hiPSCCMs) and characterized their Ca²⁺-signaling phenotype compared to WT hiPSCCMs.

Methods and Results

W4645R-RyR2 cardiomyocytes had: (1) no significant change in I_Ca magnitude or voltage-dependence; (2) slightly reduced CICR; (3) altered relaxation kinetics of Ca²⁺-transients with no change in isoproterenol sensitivity; (4) complete loss of caffeine-triggered Ca²⁺ release; (5) larger SR Ca²⁺ leak resulting in 40 % lower SR Ca²⁺ content, as determined by myocytes’ response to 4-CmC; (6) lower incidence of calcium sparks and asynchronous spontaneous SR Ca²⁺ releases.

Conclusions

W4645R-RyR2 mutation induces loss of caffeine-triggered SR Ca²⁺ release and enhances SR Ca²⁺ leak that underlie asynchronous spontaneous Ca²⁺ releases, triggering arrhythmia and impairing cardiac function.