A Novel Role of the L-Type Calcium Channel α1D Subunit as a Gatekeeper for Intracellular Zinc Signaling: Zinc Wave

Recent studies have shown that zinc ion (Zn) can behave as an intracellular signaling molecule. We previously demonstrated that mast cells stimulated through the high-affinity IgE receptor (FcεRI) rapidly release intracellular Zn from the endoplasmic reticulum (ER), and we named this phenomenon the “Zn wave”. However, the molecules responsible for releasing Zn and the roles of the Zn wave were elusive. Here we identified the pore-forming α1 subunit of the Cav1.3 (α1D) L-type calcium channel (LTCC) as the gatekeeper for the Zn wave. LTCC antagonists inhibited the Zn wave, and an agonist was sufficient to induce it. Notably, α1D was mainly localized to the ER rather than the plasma membrane in mast cells, and the Zn wave was impaired by α1D knockdown. We further found that the LTCC-mediated Zn wave positively controlled cytokine gene induction by enhancing the DNA-binding activity of NF- κB. Consistent with this finding, LTCC antagonists inhibited the cytokine-mediated delayed-type allergic reaction in mice without affecting the immediate-type allergic reaction. These findings indicated that the LTCC α1D subunit located on the ER membrane has a novel function as a gatekeeper for the Zn wave, which is involved in regulating NF-κB signaling and the delayed-type allergic reaction

The Zinc Transporter SLC39A14/ZIP14 Controls G-Protein Coupled Receptor-Mediated Signaling Required for Systemic Growth

Aberrant zinc (Zn) homeostasis is associated with abnormal control of mammalian growth, although the molecular mechanisms of Zn's roles in regulating systemic growth remain to be clarified. Here we report that the cell membrane-localized Zn transporter SLC39A14 controls G-protein coupled receptor (GPCR)-mediated signaling. Mice lacking Slc39a14 (Slc39a14-KO mice) exhibit growth retardation and impaired gluconeogenesis, which are attributable to disrupted GPCR signaling in the growth plate, pituitary gland, and liver. The decreased signaling is a consequence of the reduced basal level of cyclic adenosine monophosphate (cAMP) caused by increased phosphodiesterase (PDE) activity in Slc39a14-KO cells. We conclude that SLC39A14 facilitates GPCR-mediated cAMP-CREB signaling by suppressing the basal PDE activity, and that this is one mechanism for Zn's involvement in systemic growth processes. Our data highlight SLC39A14 as an important novel player in GPCR-mediated signaling. In addition, the Slc39a14-KO mice may be useful for studying the GPCR-associated regulation of mammalian systemic growth

Roles of Zinc Signaling in the Immune System

Zinc (Zn) is an essential micronutrient for basic cell activities such as cell growth, differentiation, and survival. Zn deficiency depresses both innate and adaptive immune responses. However, the precise physiological mechanisms of the Zn-mediated regulation of the immune system have been largely unclear. Zn homeostasis is tightly controlled by the coordinated activity of Zn transporters and metallothioneins, which regulate the transport, distribution, and storage of Zn. There is growing evidence that Zn behaves like a signaling molecule, facilitating the transduction of a variety of signaling cascades in response to extracellular stimuli. In this review, we highlight the emerging functional roles of Zn and Zn transporters in immunity, focusing on how crosstalk between Zn and immune-related signaling guides the normal development and function of immune cells

B-cell receptor strength and zinc signaling: Unraveling the role of zinc transporter ZIP10 in humoral immunity

The humoral immune response, alongside cell-mediated immunity, in which B cells play a key role, form the primary arms of the adaptive immune system. Resting mature follicular (FO) B cells in the spleen are essential for antibody-mediated immune responses. They recirculate through the blood, and are activated upon the binding of various diverse cognate antigens to the specific B cell antigen receptor (BCR) on their cell surface. With the help of T cells, the activated FO B cells undergo the germinal center (GC) reaction, which involves massive expansion and immunoglobulin (Ig) class-switch recombination (e.g. IgM to IgG1) to elicit a high-affinity antibody response against the antigens. Zinc (Zn) is essential in immunity, and in both humans and rodents, aberrant Zn homeostasis strongly disrupts the cellularity and functions of immune cells, leading to thymic and splenic atrophy, lymphopenia, and weakened cellular and humoral immunity, which increases the host’s susceptibility to various pathogens. Zn, which is transported by specific members of the Zn-transporter families, SLC39/ZIP and SLC30/ZnT, selectively fine-tunes distinct intracellular signaling events by targeting signaling molecules involved in development, growth, and immunity. Zn controls a wide range of immune signaling cascades that lead to cytokine production, antigen presentation, and the activation of kinases and transcription factors in immune cells, and disrupting the specific Zn transporter?Zn signal axis impairs cellular function. However, how Zn controls immune function, in particular the humoral immune response, is poorly understood. In this research highlight, we review our recent finding that ZIP10-Zn signaling is required in B-cell receptor signaling for the antibody-mediated immune response

How COVID-19 induces cytokine storm with high mortality

The newly emerging coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first reported in Wuhan, China, but has rapidly spread all over the world. Some COVID-19 patients encounter a severe symptom of acute respiratory distress syndrome (ARDS) with high mortality. This high severity is dependent on a cytokine storm, most likely induced by the interleukin-6 (IL-6) amplifier, which is hyper-activation machinery that regulates the nuclear factor kappa B (NF-κB) pathway and stimulated by the simultaneous activation of IL-6-signal transducer and activator of transcription 3 (STAT3) and NF-κB signaling in non-immune cells including alveolar epithelial cells and endothelial cells. We hypothesize that IL-6-STAT3 signaling is a promising therapeutic target for the cytokine storm in COVID-19, because IL-6 is a major STAT3 stimulator, particularly during inflammation. We herein review the pathogenic mechanism and potential therapeutic targets of ARDS in COVID-19 patients

The Role of the Slc39a Family of Zinc Transporters in Zinc Homeostasis in Skin

The first manifestations that appear under zinc deficiency are skin defects such as dermatitis, alopecia, acne, eczema, dry, and scaling skin. Several genetic disorders including acrodermatitis enteropathica (also known as Danbolt-Closs syndrome) and Brandt’s syndrome are highly related to zinc deficiency. However, the zinc-related molecular mechanisms underlying normal skin development and homeostasis, as well as the mechanism by which disturbed zinc homeostasis causes such skin disorders, are unknown. Recent genomic approaches have revealed the physiological importance of zinc transporters in skin formation and clarified their functional impairment in cutaneous pathogenesis. In this review, we provide an overview of the relationships between zinc deficiency and skin disorders, focusing on the roles of zinc transporters in the skin. We also discuss therapeutic outlooks and advantages of controlling zinc levels via zinc transporters to prevent cutaneous disorganization

Sjogren's syndrome-associated SNPs increase GTF2I expression in salivary gland cells to enhance inflammation development

Sjogren's syndrome (SS) is an autoimmune disease characterized by inflammation with lymphoid infiltration and destruction of the salivary glands. Although many genome-wide association studies have revealed disease-associated risk alleles, the functions of the majority of these alleles are unclear. Here, we show previously unrecognized roles of GTF2I molecules by using two SS-associated single nucleotide polymorphisms (SNPs), rs73366469 and rs117026326 (GTF2I SNPs). We found that the risk alleles of GTF2I SNPs increased GTF2I expression and enhanced nuclear factor-kappa B (NF-kappa B) activation in human salivary gland cells via the NF-kappa B p65 subunit. Indeed, the knockdown of GTF2I suppressed inflammatory responses in mouse endothelial cells and in vivo. Conversely, the over-expression of GTF2I enhanced NF-kappa B reporter activity depending on its p65-binding N-terminal leucine zipper domain. GTF2I is highly expressed in the human salivary gland cells of SS patients expressing the risk alleles. Consistently, the risk alleles of GTF2I SNPs were strongly associated with activation of the IL-6 amplifier, which is hyperactivation machinery of the NF-kappa B pathway, and lymphoid infiltration in the salivary glands of SS patients. These results demonstrated that GTF2I expression in salivary glands is increased in the presence of the risk alleles of GTF2I SNPs, resulting in activation of the NF-kappa B pathway in salivary gland cells. They also suggest that GTF2I could be a new therapeutic target for SS

The LTCC-mediated Zn wave is involved in cytokine gene inductions.

<p>(A) The FcεRI-mediated inductions of <i>Il6</i> and <i>Tnfa</i> transcription upon antigen stimulation for the indicated time in BMMCs with or without pretreatment with 100 µM Verapamil were determined by semi-quantitative RT-PCR. (B) The mRNA levels of <i>Il6</i> and <i>Tnfa</i> upon antigen stimulation for 60 min in control (siControl) or α_1D siRNA-treated (si α_1D) BMMCs were determined by semi-quantitative RT-PCR. (C) The level of degranulation after 30 min of antigen stimulation in BMMCs with or without pretreatment with 100 µM Verapamil was determined by measuring the β-hexosaminidase activity. (D) Level of degranulation after 30 min of antigen stimulation in siControl and α1_D siRNA-treated BMMCs. N.S., not significant, *<i>P</i><0.05, **<i>P</i><0.01, two-tailed Student’s <i>t</i>-test.</p