Expression of signal-transducing adaptor protein-1 attenuates experimental autoimmune hepatitis via down-regulating activation and homeostasis of invariant natural killer T cells

STAP-1-derived peptide suppresses TCR-mediated T cell activation and ameliorates immune diseases by inhibiting STAP-1-LCK binding

Signal-transducing adaptor protein-1 (STAP-1) is an adaptor protein specifically expressed in immune cells, such as T cells. We previously demonstrated that STAP-1 positively upregulates T cell receptor (TCR)-mediated T cell activation by interacting with LCK and phospholipase C-γ1 and affecting autoimmune demyelination and airway inflammation. In this study, we aimed to generate a new STAP-1-derived peptide, iSP1, to inhibit the STAP-1-LCK interaction. We also analyzed its function in vitro and in vivo. iSP1 successfully interfered with STAP-1-LCK binding and suppressed TCR-mediated signal transduction, interleukin-2 production, and human and murine T cell proliferation. Additionally, iSP1 prevented the progression of experimental autoimmune encephalomyelitis by inhibiting Th1 and Th17 cell infiltration. Our findings suggest iSP1 as a new therapeutic immunomodulatory agent for T cell-mediated autoimmune diseases.

Whole genome resequencing revealed genomic variants and functional pathways related to adaptation in Indian yak populations

The present study aims to identify genomic variants through a whole genome sequencing (WGS) approach and uncover biological pathways associated with adaptation and fitness in Indian yak populations. A total of 30 samples (10 from each population) were included from Arunachali, Himachali and Ladakhi yak populations. WGS analysis revealed a total of 32171644, 27260825, and 32632460 SNPs and 4865254, 4429941, and 4847513 Indels in the Arunachali, Himachali, and Ladakhi yaks, respectively. Genes such as RYR2, SYNE2, BOLA, HF1, and the novel transcript ENSBGRG00000011079 were found to have the maximum number of high impact variants in all three yak populations, and might play a major role in local adaptation. Functional enrichment analysis of genes harboring high impact SNPs revealed overrepresented pathways related to response to stress, immune system regulation, and high-altitude adaptation. This study provides comprehensive information about genomic variants and their annotation in Indian yak populations, thus would serve as a data resource for researchers working on the yaks. Furthermore, it could be well exploited for better yak conservation strategies by estimating population genetics parameters viz., effective population size, inbreeding, and observed and expected heterozygosity.

Role of Signal-Transducing Adaptor Protein-1 for T Cell Activation and Pathogenesis of Autoimmune Demyelination and Airway Inflammation

Signal-transducing adaptor protein (STAP)-1 is an adaptor protein that is widely expressed in T cells. In this article, we show that STAP-1 upregulates TCR-mediated T cell activation and T cell-mediated airway inflammation. Using STAP-1 knockout mice and STAP-1-overexpressing Jurkat cells, we found that STAP-1 enhanced TCR signaling, resulting in increased calcium mobilization, NFAT activity, and IL-2 production. Upon TCR engagement, STAP-1 binding to ITK promoted formation of ITK-LCK and ITK-phospholipase Cγ1 complexes to induce downstream signaling. Consistent with the results, STAP-1 deficiency reduced the severity of symptoms in experimental autoimmune encephalomyelitis. Single-cell RNA-sequencing analysis revealed that STAP-1 is essential for accumulation of T cells and Ifng and Il17 expression in spinal cords after experimental autoimmune encephalomyelitis induction. Th1 and Th17 development was also attenuated in STAP-1 knockout naive T cells. Taken together, STAP-1 enhances TCR signaling and plays a role in T cell-mediated immune disorders.

Relationship between STAP1 methylation in peripheral blood T cells and the clinicopathological characteristics and prognosis of patients within 5-cm diameter HCC

BACKGROUND

The aim of this study is to explore the methylation of signal transduction adaptor protein 1 (STAP1) in peripheral blood T cells as a prognostic marker for hepatocellular carcinoma (HCC) ≤5 cm.

METHODS

A total of 66 HCC patients who visited our hospital from November 2012 to June 2016 were retrospectively analyzed, and 55 patients who met the inclusion and exclusion criteria were studied. Clinical and pathological data were collected from all patients to detect STAP1 methylation. STAP1 methylation expression was analyzed in HCC patients ≤5 cm with different clinicopathological features; univariate and independent prognostic factors were analyzed in HCC patients; and the relationship between STAP1 methylation expression and prognosis was analyzed in HCC patients.

RESULTS

There was no significant difference in STAP1 methylation expression between patients with different gender, age, history of alcoholism, history of liver cirrhosis, recurrence, 3-year OS, 5-year OS, treatment, number of tumors, tumor diameter, HBV-DNA, HBSAg, Hbe-Ag expression, and AFP level (P>0.05); however, there was significant difference in STAP1 methylation expression between patients with different survival, 3-year DFS, and 5-year DFS (P<0.05). Multivariate Cox regression analysis showed that recurrence and STAP1 methylation were independent factors for OS and DFS (P<0.05). Kaplan-Meier survival curve results showed that the median survival time, OS, and DFS of STAP1 hypermethylation expression were shorter than those of hypomethylation (P<0.05).

CONCLUSIONS

STAP1 methylation in peripheral blood T cells serves as a potential prognostic marker for HCC ≤5 cm.

Possible Therapeutic Applications of Targeting STAP Proteins in Cancer

The signal-transducing adaptor protein (STAP) family, including STAP-1 and STAP-2, contributes to a variety of intracellular signaling pathways. The proteins in this family contain typical structures for adaptor proteins, such as Pleckstrin homology in the N-terminal regions and SRC homology 2 domains in the central regions. STAP proteins bind to inhibitor of kappaB kinase complex, breast tumor kinase, signal transducer and activator of transcription 3 (STAT3), and STAT5, during tumorigenesis and inflammatory/immune responses. STAP proteins positively or negatively regulate critical steps in intracellular signaling pathways through individually unique mechanisms. This article reviews the roles of the novel STAP family and the possible therapeutic applications of targeting STAP proteins in cancer.

Signal-transducing adaptor protein-1 and protein-2 in hematopoiesis and diseases

Inflammatory and immune signals are involved in stressed hematopoiesis under myeloablation, infection, chronic inflammation, and aging. These signals also affect malignant pathogenesis, and the dysregulated immune environment which causes the resistance to treatment. On activation, various types of protein tyrosine kinases in the cytoplasm mediate the cascade, leading to the transcription of target genes in the nucleus. Adaptor molecules are commonly defined as proteins that lack enzymatic activity, DNA-binding or receptor functions and possess protein-protein or protein-lipid interaction domains. By binding to specific domains of signaling molecules, adaptor proteins adjust the signaling responses after the ligation of receptors of soluble factors, including cytokines, chemokines, and growth factors, as well as pattern recognition receptors such as toll-like receptors. The signal-transducing adaptor protein (STAP) family regulates various intracellular signaling pathways. These proteins have a pleckstrin homology domain in the N-terminal region and an SRC-homology 2-like domain in the central region, representing typical binding structures as adapter proteins. Following the elucidation of the effects of STAPs on terminally differentiated immune cells, such as macrophages, T cells, mast cells, and basophils, recent findings have indicated the critical roles of STAP-2 in B-cell progenitor cells in marrow under hematopoietic stress and STAP-1 and -2 in BCR-ABL-transduced leukemogenesis. In this review, we focus on the role of STAPs in the bone marrow.

Signal-transducing adaptor protein-2 has a nonredundant role for IL-33-triggered mast cell activation

Signal-transducing adaptor protein (STAP)-2 is one of the STAP family adaptor proteins and ubiquitously expressed in a variety types of cells. Although STAP-2 is required for modification of FcεRI signal transduction in mast cells, other involvement of STAP-2 in mast cell functions is unknown, yet. In the present study, we mainly investigated functional roles of STAP-2 in IL-33-induced mast cell activation. In STAP-2-deficient, but not STAP-1-deficient, mast cells, IL-33-induced IL-6 and TNF-α production was significantly decreased compared with that of wild-type mast cells. In addition, STAP-2-deficiency greatly reduced TLR4-mediated mast cell activation and cytokine production. For the mechanisms, STAP-2 directly binds to IKKα after IL-33 stimulation, leading to elevated NF-κB activity. In conclusion, STAP-2, but not STAP-1, participates in IL-33-induced mast cells activation.

Positive interactions between STAP-1 and BCR-ABL influence chronic myeloid leukemia cell proliferation and survival

Chronic myeloid leukemia (CML) is a clonal disease characterized by the presence of the Philadelphia chromosome and its oncogenic product, BCR-ABL, which activates multiple pathways involved in cell survival, growth promotion, and disease progression. We recently reported that signal-transducing adaptor protein 1 (STAP-1) is upregulated in CML stem cells (LSCs) and functions to reduce the apoptosis of CML LSCs by upregulating the STAT5-downstream anti-apoptotic genes. In this study, we demonstrate the detailed molecular interactions among BCR-ABL, STAP-1, and signal transducer and activator of transcription 5 (STAT5). Studies with deletion mutants have revealed that STAP-1 interacts with BCR-ABL and STAT5a through its SH2 and PH domains, respectively, suggesting the possible role of STAP-1 as a scaffold protein. Furthermore, the binding of STAP-1 to BCR-ABL stabilizes the BCR-ABL protein in CML cells. Since STAP-1 is highly expressed in CML cells, we also analyzed the STAP-1 promoter activity using a luciferase reporter construct and found that NFATc1 is involved in activating the STAP-1 promoter and inducing STAP-1 mRNA expression. Our results demonstrate that STAP-1 contributes to the BCR-ABL/STAT5 and BCR-ABL/Ca²⁺/NFAT signals to induce proliferation and STAP-1 mRNA expression in CML cells, respectively.