Disrupted Ca^(2+) h homeostasis and immunodeficiency in patients with functional IP_(3) receptor subtype 3 defects

Calcium signaling is essential for lymphocyte activation, with genetic disruptions of store-operated calcium (Ca^(2+)) entry resulting in severe immunodeficiency. The inositol 1,4,5-trisphosphate receptor (IP_(3)R), a homo- or heterotetramer of the IP_(3)R1-3 isoforms, amplifies lymphocyte signaling by releasing Ca^(2+) from endoplasmic reticulum stores following antigen stimulation. Although knockout of all IP_(3)R isoforms in mice causes immunodeficiency, the seeming redundancy of the isoforms is thought to explain the absence of variants in human immunodeficiency. In this study, we identified compound heterozygous variants of ITPR3 (a gene encoding IP_(3)R subtype 3) in two unrelated Caucasian patients presenting with immunodeficiency. To determine whether ITPR3 variants act in a nonredundant manner and disrupt human immune responses, we characterized the Ca^(2+) signaling capacity, the lymphocyte response, and the clinical phenotype of these patients. We observed disrupted Ca^(2+) signaling in patient-derived fibroblasts and immune cells, with abnormal proliferation and activation responses following T-cell receptor stimulation. Reconstitution of IP_(3)R3 in IP_(3)R knockout cell lines led to the identification of variants as functional hypomorphs that showed reduced ability to discriminate between homeostatic and induced states, validating a genotype–phenotype link. These results demonstrate a functional link between defective endoplasmic reticulum Ca^(2+) channels and immunodeficiency and identify IP_(3)Rs as diagnostic targets for patients with specific inborn errors of immunity. These results also extend the known cause of Ca^(2+)-associated immunodeficiency from store-operated entry to impaired Ca^(2+) mobilization from the endoplasmic reticulum, revealing a broad sensitivity of lymphocytes to genetic defects in Ca^(2+) signaling.

Polycomb chromobox Cbx2 enhances antiviral innate immunity by promoting Jmjd3-mediated demethylation of H3K27 at the Ifnb promoter

Polycomb chromobox(CBX)proteins regulate gene transcription by maintaining chromatin states,which guide a variety of biological processes.Now,epigenetic regulation of innate immune response is an emerging field.However,the role of CBX proteins in innate immunity remains unclear.We confirmed that the expression of CBX family proteins,especially Cbx2,was decreased in macrophages upon viral infection,and then we investigated the role of Cbx2 in the antiviral immune response.Silencing or knockdown of Cbx2 in macrophages inhibited virus-induced production of IFNp.Furthermore,heterozygous Cbx2 knockout were susceptible to VSV challenge.Mechanistically,Cbx2 binds to and recruits Jmjd3 to the Ifnb promoter,leading to demethylation of H3K27me3 and increased transcription of IFN-β.Together,our study reveals a nontraditional function of a Cbx protein and adds new insight into the epigenetic regulation of antiviral innate immunity.

ATP6V0d2 mediates leucine-induced mTORCI activation and polarization of macrophages

Dear Editor, mTORCI, as a center regulatory hub of metabolism, senses the cellular energy status, nutrition and extracellular stimuli and regulates cell growth, differentiation and functions of immune cells (Powell et al., 2012). Lysosomal localization of key signal comp orients is critical for mTORCI activati on: mTORCI activation requires co-localization of activated Rheb and mTORCI to the lysosome membrane (Buerger et al., 2006). Signals in eluding growth factors, cellular stresses and energy levels act on the disruption the formation of tuberous sclerosis complex (TSC) complex, comprised of TSC1, TSC2 and TBC1D7, which leads to the translocation and activation of Rheb on the lysosome membrane (Dibble et al., 2012). In response to nutrient levels, specifically the availability of amino acids and glucose (Efeyan et al., 2013), mTORCI is recruited to the lysosomal surface by Rag GTPases that are heterodimers of RagA or RagC bound to RagB or RagD. Multiple protein complexes have been implicated in regulation of mTORCI upon nutrient sensing including Ragulator, GATOR1, GATOR2, KICSTOR and vacuolar ATPases (Wolfson et al., 2017). Vacuolar ATPases are large multiple-protein complexes that acidify the lysosome and may mediate additional functions independent of their proton pump activity (Nishi and Forgac, 2002).