OCaR1 endows exocytic vesicles with autoregulatory competence by preventing uncontrolled Ca2+ release, exocytosis, and pancreatic tissue damage.

Regulated exocytosis is initiated by increased Ca2+ concentrations in close spatial proximity to secretory granules, which is effectively prevented when the cell is at rest. Here we showed that exocytosis of zymogen granules in acinar cells was driven by Ca2+ directly released from acidic Ca2+ stores including secretory granules through NAADP-activated two-pore channels (TPCs). We identified OCaR1 (encoded by Tmem63a) as an organellar Ca2+ regulator protein integral to the membrane of secretory granules that controlled Ca2+ release via inhibition of TPC1 and TPC2 currents.

Combining mass spectrometry and genetic labeling in mice to report TRP channel expression.

Transient receptor potential (TRP) ion channels play important roles in fundamental biological processes throughout the body of humans and mice. TRP channel dysfunction manifests in different disease states, therefore, these channels may represent promising therapeutic targets in treating these conditions. Many TRP channels are expressed in several organs suggesting multiple functions and making it challenging to untangle the systemic pathophysiology of TRP dysfunction.

Additional data for the mouse TRPV6 expression atlas.

To identify TRPV6 expression in the whole mouse with a cellular resolution we took advantage of TRPV6-IRES-Cre knock-in mice crossed with the enhanced ROSA26-τGFP reporter line. In the resulting TRPV6-IC/eR26-τGFP animals, TRPV6-expressing cells are labeled with τGFP. Data were collected from organs prepared from fixed experimental adult and juvenile TRPV6-IC/eR26τGFP and Cre-negative eR26-τGFP control animals of both sexes.

IP3-dependent Ca signals are tightly controlled by Cavβ3, but not by Cavβ1, 2 and 4.

Independent of its function as a subunit of voltage-gated Ca channels, the Cavβ3 subunit desensitizes fibroblasts and pancreatic β-cells to low concentrations of inositol-1,4,5-trisphosphate (IP3). This alters agonist-induced Ca signaling and cellular functions, for example, insulin secretion and wound healing. A total of four Cavβ subunits exist, Cavβ1, Cavβ2, Cavβ3, and Cavβ4.

Mutations That Affect the Surface Expression of TRPV6 Are Associated with the Upregulation of Serine Proteases in the Placenta of an Infant.

Recently, we reported a case of an infant with neonatal severe under-mineralizing skeletal dysplasia caused by mutations within both alleles of the gene. One mutation results in an in frame stop codon (Rstop) that leads to a truncated, nonfunctional TRPV6 channel, and the second in a point mutation (GR) that, surprisingly, does not affect the Ca permeability of TRPV6. We mimicked the subunit composition of the unaffected heterozygous parent and child by coexpressing the TRPV6 GR and Rstop mutants and combinations with wild type TRPV6.

A TRPV6 expression atlas for the mouse.

The transient receptor potential vanilloid 6 (TRPV6) channel is highly Ca-selective and has been implicated in mediating transcellular Ca transport and thus maintaining the Ca balance in the body. To characterize its physiological function(s), a detailed expression profile of the TRPV6 channel throughout the body is essential. Capitalizing on a recently established murine Trpv6-reporter strain, we identified primary TRPV6 channel-expressing cells in an organism-wide manner.

Transient Receptor Potential Vanilloid 6 (TRPV6) Proteins Control the Extracellular Matrix Structure of the Placental Labyrinth.

Calcium-selective transient receptor potential Vanilloid 6 (TRPV6) channels are expressed in fetal labyrinth trophoblasts as part of the feto-maternal barrier, necessary for sufficient calcium supply, embryo growth, and bone development during pregnancy. Recently, we have shown a less- compact labyrinth morphology of deficient placentae, and reduced Ca uptake of primary trophoblasts upon functional deletion of TRPV6. trophoblasts show a distinct calcium-dependent phenotype.

Control of Insulin Release by Transient Receptor Potential Melastatin 3 (TRPM3) Ion Channels.

Background/aims: The release of insulin in response to increased levels of glucose in the blood strongly depends on Ca influx into pancreatic beta cells by the opening of voltage-gated Ca channels. Transient Receptor Potential Melastatin 3 proteins build Ca permeable, non-selective cation channels serving as pain sensors of noxious heat in the peripheral nervous system. TRPM3 channels are also strongly expressed in pancreatic beta cells that respond to the TRPM3 agonist pregnenolone sulfate with Ca influx and increased insulin release.

Identification of signal peptide features for substrate specificity in human Sec62/Sec63-dependent ER protein import.

In mammalian cells, one-third of all polypeptides are integrated into the membrane or translocated into the lumen of the endoplasmic reticulum (ER) via the Sec61 channel. While the Sec61 complex facilitates ER import of most precursor polypeptides, the Sec61-associated Sec62/Sec63 complex supports ER import in a substrate-specific manner. So far, mainly posttranslationally imported precursors and the two cotranslationally imported precursors of ERj3 and prion protein were found to depend on the Sec62/Sec63 complex in vitro.

Variants That Affect Function of Calcium Channel TRPV6 Are Associated With Early-Onset Chronic Pancreatitis.

Background & Aims: Changes in pancreatic calcium levels affect secretion and might be involved in development of chronic pancreatitis (CP). We investigated the association of CP with the transient receptor potential cation channel subfamily V member 6 gene (TRPV6), which encodes a Ca-selective ion channel, in an international cohort of patients and in mice.

Methods: We performed whole-exome DNA sequencing from a patient with idiopathic CP and from his parents, who did not have CP.

TRPC channels regulate Ca2+-signaling and short-term plasticity of fast glutamatergic synapses.

Transient receptor potential (TRP) proteins form Ca2+-permeable, nonselective cation channels, but their role in neuronal Ca2+ homeostasis is elusive. In the present paper, we show that TRPC channels potently regulate synaptic plasticity by changing the presynaptic Ca2+-homeostasis of hippocampal neurons. Specifically, loss of TRPC1/C4/C5 channels decreases basal-evoked secretion, reduces the pool size of readily releasable vesicles, and accelerates synaptic depression during high-frequency stimulation (HFS).

TRPV6 and Ca1.3 Mediate Distal Small Intestine Calcium Absorption Before Weaning.

Background & Aims: Intestinal Ca absorption early in life is vital to achieving optimal bone mineralization. The molecular details of intestinal Ca absorption have been defined in adults after peak bone mass is obtained, but they are largely unexplored during development. We sought to delineate the molecular details of transcellular Ca absorption during this critical period.

Trpc5 deficiency causes hypoprolactinemia and altered function of oscillatory dopamine neurons in the arcuate nucleus.

Dopamine neurons of the hypothalamic arcuate nucleus (ARC) tonically inhibit the release of the protein hormone prolactin from lactotropic cells in the anterior pituitary gland and thus play a central role in prolactin homeostasis of the body. Prolactin, in turn, orchestrates numerous important biological functions such as maternal behavior, reproduction, and sexual arousal. Here, we identify the canonical transient receptor potential channel Trpc5 as an essential requirement for normal function of dopamine ARC neurons and prolactin homeostasis.

The Evolution of Erythrocytes Becoming Red in Respect to Fluorescence.

Very young red blood cells, namely reticulocytes, can be quite easily recognized and labeled by cluster of differentiation antibodies (CD71, transferrin receptor) or by staining remnant RNA with thiazol orange. In contrast, age specific erythrocyte labeling is more difficult in later periods of their life time. While erythrocytes contain band 4.

Activation of the calcium sensing receptor attenuates TRPV6-dependent intestinal calcium absorption.

Plasma calcium (Ca2+) is maintained by amending the release of parathyroid hormone and through direct effects of the Ca2+ sensing receptor (CaSR) in the renal tubule. Combined, these mechanisms alter intestinal Ca2+ absorption by modulating 1,25-dihydroxy vitamin D3 production, bone resorption, and renal Ca2+ excretion. The CaSR is a therapeutic target in the treatment of secondary hyperparathyroidism and hypocalcemia a common complication of calcimimetic therapy.

Maternal Transient Receptor Potential Vanilloid 6 (Trpv6) Is Involved In Offspring Bone Development.

Embryonic growth and bone development depend on placental Ca transport across the feto-maternal barrier to supply minerals to the fetus. The individual factors and cellular mechanisms that regulate placental Ca transfer, however, are only beginning to emerge. We find that the Ca -selective transient receptor potential vanilloid 6 (TRPV6) channel is expressed in trophoblasts of the fetal labyrinth, in the yolk sac, and in the maternal part of the placenta.

Heteromeric channels formed by TRPC1, TRPC4 and TRPC5 define hippocampal synaptic transmission and working memory.

Canonical transient receptor potential (TRPC) channels influence various neuronal functions. Using quantitative high-resolution mass spectrometry, we demonstrate that TRPC1, TRPC4, and TRPC5 assemble into heteromultimers with each other, but not with other TRP family members in the mouse brain and hippocampus. In hippocampal neurons from -triple-knockout () mice, lacking any TRPC1-, TRPC4-, or TRPC5-containing channels, action potential-triggered excitatory postsynaptic currents (EPSCs) were significantly reduced, whereas frequency, amplitude, and kinetics of quantal miniature EPSC signaling remained unchanged.

TRPC1- and TRPC3-dependent Ca signaling in mouse cortical astrocytes affects injury-evoked astrogliosis in vivo.

Following brain injury astrocytes change into a reactive state, proliferate and grow into the site of lesion, a process called astrogliosis, initiated and regulated by changes in cytoplasmic Ca . Transient receptor potential canonical (TRPC) channels may contribute to Ca influx but their presence and possible function in astrocytes is not known. By RT-PCR and RNA sequencing we identified transcripts of Trpc1, Trpc2, Trpc3, and Trpc4 in FACS-sorted glutamate aspartate transporter (GLAST)-positive cultured mouse cortical astrocytes and subcloned full-length Trpc1 and Trpc3 cDNAs from these cells.

Functional Characterization of Transient Receptor Potential (TRP) Channel C5 in Female Murine Gonadotropes.

Gonadotrope cells in the anterior pituitary gland secrete gonadotropins regulating gonadal function in mammals. Recent results have implicated transient receptor potential (TRP) cation channels in pituitary physiology; however, if and how TRP channels contribute to gonadotrope function is not known. Here, we report that 14 out of 28 TRP channels encoded in the mouse genome are expressed in murine gonadotropes with highest expression levels found for canonical TRP (TRPC) channel 5 in juvenile females.

Murine Autoimmune Optic Neuritis Is Not Phenotypically Altered by the Retinal Degeneration 8 Mutation.

Purpose: To investigate whether the presence of the retinal degeneration 8 (rd8) mutation in C57BL/6 mice alters the phenotype of autoimmune optic neuritis (AON).

Methods: C57BL/6J and C57BL/6N mice were genotyped for the rd8 mutation and fundus analyses and examination of retinal layer morphology were performed in vivo by scanning laser ophthalmoscopy and optical coherence tomography. Visual function was assessed by recording electroretinographs, and visual evoked potentials and retinae and optic nerves were assessed histopathologically.

Essential roles for Cavβ2 and Cav1 channels in thymocyte development and T cell homeostasis.

Calcium ions (Ca(2+)) are important in numerous signal transduction processes, including the development and differentiation of T cells in the thymus. We report that thymocytes have multiple types of pore-forming α subunits and regulatory β subunits that constitute voltage-gated Ca(2+) (Cav) channels. In mice, T cell-specific deletion of the gene encoding the β2 regulatory subunit of Cav channels (Cacnb2) reduced the abundances of the channels Cav1.

Influence of the β2-Subunit of L-Type Voltage-Gated Cav Channels on the Structural and Functional Development of Photoreceptor Ribbon Synapses.

Purpose: The cacnb2 gene encodes the β2 subunit (Cavβ2) of voltage-gated Ca2+ channels in photoreceptors, and its targeted deletion in mice has previously been shown to cause altered retinal morphology and synaptic transmission. The purpose of this study was to provide a detailed morphologic study combined with experiments on the altered functions of photoreceptor ribbon synapses lacking Cavβ2.

Methods: A cacnb2-deficient mouse strain was generated and deletion of the Cavβ2 in the retina documented by biochemical and immunhistochemical approaches.

Altered synaptic transmission at olfactory and vomeronasal nerve terminals in mice lacking N-type calcium channel Cav2.2.

We investigated the role of voltage-activated calcium (Cav) channels for synaptic transmission at mouse olfactory and vomeronasal nerve terminals at the first synapse of the main and accessory olfactory pathways, respectively. We provided evidence for a central role of the N-type Cav channel subunit Cav2.2 in presynaptic transmitter release at these synapses.