Inositol 1,4,5-Trisphosphate Receptor Mutations Associated with Human Disease: Insights into Receptor Function and Dysfunction.

Inositol 1,4,5-trisphosphate receptors (IPRs) are ubiquitous intracellular Ca2+ release channels. Their activation, subcellular localization, abundance, and regulation play major roles in defining the spatiotemporal characteristics of intracellular Ca2+ signals, which are in turn fundamental to the appropriate activation of effectors that control a myriad of cellular events. Over the past decade, ∼100 mutations in s associated with human diseases have been documented.

Ca2+ tunneling architecture and function are important for secretion.

Ca2+ tunneling requires both store-operated Ca2+ entry (SOCE) and Ca2+ release from the endoplasmic reticulum (ER). Tunneling expands the SOCE microdomain through Ca2+ uptake by SERCA into the ER lumen where it diffuses and is released via IP3 receptors. In this study, using high-resolution imaging, we outline the spatial remodeling of the tunneling machinery (IP3R1; SERCA; PMCA; and Ano1 as an effector) relative to STIM1 in response to store depletion.

Loss of STIM1 and STIM2 in salivary glands disrupts ANO1 function but does not induce Sjogren's disease.

Ca2+ signaling via the store operated Ca2+ entry (SOCE) mediated by STIM1 and STIM2 proteins and the ORAI1 Ca2+ channel is important in saliva fluid secretion and has been associated with Sjogren's disease (SjD). However, there are no studies addressing STIM1/2 dysfunction in salivary glands or SjD in animal models. We report that mice lacking Stim1 and Stim2 (Stim1/2K14Cre(+)) in salivary glands exhibited reduced Ca2+ levels and hyposalivate.

CISD2 counteracts the inhibition of ER-mitochondrial calcium transfer by anti-apoptotic BCL-2.

CISD2, a 2Fe2S cluster domain-containing protein, is implicated in Wolfram syndrome type 2, longevity and cancer. CISD2 is part of a ternary complex with IP receptors (IPRs) and anti-apoptotic BCL-2 proteins and enhances BCL-2's anti-autophagic function. Here, we examined how CISD2 impacted the function of BCL-2 in apoptosis and in controlling IPR-mediated Ca signaling.

Dysregulated Ca signaling, fluid secretion, and mitochondrial function in a mouse model of early Sjögren's disease.

The molecular mechanisms leading to saliva secretion are largely established, but factors that underlie secretory hypofunction, specifically related to the autoimmune disease Sjögren's syndrome (SS) are not fully understood. A major conundrum is the lack of association between the severity of salivary gland immune cell infiltration and glandular hypofunction. SS-like disease was induced by treatment with DMXAA, a small molecule agonist of murine STING.

Functional investigation of a putative calcium-binding site involved in the inhibition of inositol 1,4,5-trisphosphate receptor activity.

A wide variety of factors influence inositol 1,4,5-trisphosphate (IP ) receptor (IP R) activity resulting in modulation of intracellular Ca release. This regulation is thought to define the spatio-temporal patterns of Ca signals necessary for the appropriate activation of downstream effectors. The binding of both IP and Ca are obligatory for IP R channel opening, however, Ca regulates IP R activity in a biphasic manner.

Tetrameric, active PKM2 inhibits IP receptors, potentially requiring GRP75 as an additional interaction partner.

Pyruvate kinase M2 (PKM2) is a key glycolytic enzyme interacting with the inositol 1,4,5-trisphosphate receptor (IPR). This interaction suppresses IPR-mediated cytosolic [Ca] rises. As PKM2 exists in monomeric, dimeric and tetrameric forms displaying different properties including catalytic activity, we investigated the molecular determinants of PKM2 enabling its interaction with IPRs.

Neuronal and hormonal control of Ca signalling in exocrine glands: insight from in vivo studies.

Fluid and enzyme secretion from exocrine glands is initiated by Ca signalling in acinar cells and is activated by external neural or hormonal signals. A wealth of information has been derived from studies in acutely isolated exocrine cells but Ca signalling has until recently not been studied in undisrupted intact tissue in live mice. Our in vivo observations using animals expressing genetically encoded Ca indicators in specific cell types in exocrine glands revealed both similarities to and differences from the spatiotemporal characteristics previously reported in isolated cells.

A PACAP-activated network for secretion requires coordination of Ca influx and Ca mobilization.

Chromaffin cells of the adrenal medulla transduce sympathetic nerve activity into stress hormone secretion. The two neurotransmitters principally responsible for coupling cell stimulation to secretion are acetylcholine and pituitary adenylate activating polypeptide (PACAP). In contrast to acetylcholine, PACAP evokes a persistent secretory response from chromaffin cells.

Dysregulated Ca signaling, fluid secretion, and mitochondrial function in a mouse model of early Sjögren's syndrome.

Saliva is essential for oral health. The molecular mechanisms leading to physiological fluid secretion are largely established, but factors that underlie secretory hypofunction, specifically related to the autoimmune disease Sjögren's syndrome (SS) are not fully understood. A major conundrum is the lack of association between the severity of inflammatory immune cell infiltration within the salivary glands and glandular hypofunction.

A mathematical model of ENaC and Slc26a6 regulation by CFTR in salivary gland ducts.

Cystic fibrosis (CF) is a genetic disease caused by the mutations of cystic fibrosis transmembrane conductance regulator (), the cystic fibrosis transmembrane conductance regulator gene. Cftr is a critical ion channel expressed in the apical membrane of mouse salivary gland striated duct cells. Although Cftr is primarily a Cl channel, its knockout leads to higher salivary Cl and Na concentrations and lower pH.

Loss of STIM1 and STIM2 in salivary glands disrupts ANO1 function but does not induce Sjogren's disease.

Sjogren's disease (SjD) is an autoimmune disease characterized by xerostomia (dry mouth), lymphocytic infiltration into salivary glands and the presence of SSA and SSB autoantibodies. Xerostomia is caused by hypofunction of the salivary glands and has been involved in the development of SjD. Saliva production is regulated by parasympathetic input into the glands initiating intracellular Ca signals that activate the store operated Ca entry (SOCE) pathway eliciting sustained Ca influx.

A PACAP-activated network for secretion requires coordination of Ca influx and Ca mobilization.

Chromaffin cells of the adrenal medulla transduce sympathetic nerve activity into stress hormone secretion. The two neurotransmitters principally responsible for coupling cell stimulation to secretion are acetylcholine and pituitary adenylate activating polypeptide (PACAP). In contrast to acetylcholine, PACAP evokes a persistent secretory response from chromaffin cells.

IP3RPEP6, a novel peptide inhibitor of IP receptor channels that does not affect connexin-43 hemichannels.

Aim: Inositol 1,4,5-trisphosphate receptors (IP Rs) are intracellular Ca -release channels with crucial roles in cell function. Current IP R inhibitors suffer from off-target effects and poor selectivity towards the three distinct IP R subtypes. We developed a novel peptide inhibitor of IP Rs and determined its effect on connexin-43 (Cx43) hemichannels, which are co-activated by IP R stimulation.

Pacing intracellular Ca signals in exocrine acinar cells.

An increase in intracellular [Ca ] in exocrine acinar cells resident in the salivary glands or pancreas is a fundamental event that drives fluid secretion and exocytosis of proteins. Stimulation with secretagogues initiates Ca signals with precise spatiotemporal properties thought to be important for driving physiological output. Both in vitro, in acutely isolated acini, and in vivo, in animals expressing genetically encoded indicators, individual cells appear specialized to initiate Ca signals upon stimulation.

Two-pore channel-2 and inositol trisphosphate receptors coordinate Ca signals between lysosomes and the endoplasmic reticulum.

Lysosomes and the endoplasmic reticulum (ER) are Ca stores mobilized by the second messengers NAADP and IP, respectively. Here, we establish Ca signals between the two sources as fundamental building blocks that couple local release to global changes in Ca. Cell-wide Ca signals evoked by activation of endogenous NAADP-sensitive channels on lysosomes comprise both local and global components and exhibit a major dependence on ER Ca despite their lysosomal origin.

Inflammation, lipid dysregulation, and transient receptor potential cation channel subfamily V member 4 signaling perpetuate chronic vulvar pain.

Localized provoked vulvodynia is characterized by chronic vulvar pain that disrupts every aspect of the patient's life. Pain is localized to the vulvar vestibule, a specialized ring of tissue immediately surrounding the vaginal opening involved in immune defense. In this article, we show inflammation is the critical first step necessary for the generation of pain signals in the vulva.

A multiple-oscillator mechanism underlies antigen-induced Ca oscillations in Jurkat T-cells.

T-cell receptor stimulation triggers cytosolic Ca signaling by inositol-1,4,5-trisphosphate (IP)-mediated Ca release from the endoplasmic reticulum (ER) and Ca entry through Ca release-activated Ca (CRAC) channels gated by ER-located stromal-interacting molecules (STIM1/2). Physiologically, cytosolic Ca signaling manifests as regenerative Ca oscillations, which are critical for nuclear factor of activated T-cells-mediated transcription. In most cells, Ca oscillations are thought to originate from IP receptor-mediated Ca release, with CRAC channels indirectly sustaining them through ER refilling.

Structural and functional analysis of salivary intercalated duct cells reveals a secretory phenotype.

Currently, all salivary ducts (intercalated, striated and collecting) are assumed to function broadly in a similar manner, reclaiming ions that were secreted by the secretory acinar cells while preserving fluid volume and delivering saliva to the oral cavity. Nevertheless, there has been minimal investigation into the structural and functional differences between distinct types of salivary duct cells. Therefore, in this study, the expression profile of proteins involved in stimulus-secretion coupling, as well as the function of the intercalated duct (ID) and striated duct cells, was examined.

Regulation of store-operated Ca entry by IP receptors independent of their ability to release Ca.

Loss of endoplasmic reticular (ER) Ca activates store-operated Ca entry (SOCE) by causing the ER localized Ca sensor STIM to unfurl domains that activate Orai channels in the plasma membrane at membrane contact sites (MCS). Here, we demonstrate a novel mechanism by which the inositol 1,4,5 trisphosphate receptor (IPR), an ER-localized IP-gated Ca channel, regulates neuronal SOCE. In human neurons, SOCE evoked by pharmacological depletion of ER-Ca is attenuated by loss of IPRs, and restored by expression of IPRs even when they cannot release Ca, but only if the IPRs can bind IP.

Tools for Quantitative Analysis of Calcium Signaling Data Using Jupyter-Lab Notebooks.

Calcium signaling data analysis has become increasing complex as the size of acquired datasets increases. In this paper we present a Ca signaling data analysis method that employs custom written software scripts deployed in a collection of Jupyter-Lab "notebooks" which were designed to cope with this complexity. The notebook contents are organized to optimize data analysis workflow and efficiency.

Understanding IPR channels: From structural underpinnings to ligand-dependent conformational landscape.

Inositol 1,4,5-trisphosphate receptors (IPRs) are ubiquitously expressed large-conductance Ca-permeable channels predominantly localized to the endoplasmic reticulum (ER) membranes of virtually all eukaryotic cell types. IPRs work as Ca signaling hubs through which diverse extracellular stimuli and intracellular inputs are processed and then integrated to result in delivery of Ca from the ER lumen to generate cytosolic Ca signals with precise temporal and spatial properties. IPR-mediated Ca signals control a vast repertoire of cellular functions ranging from gene transcription and secretion to the more enigmatic brain activities such as learning and memory.