CISH

CISH (CIS-1) is a cytokine-inducible SH2-domain protein that functions as a negative-feedback inhibitor across multiple cytokine signaling pathways, dampening STAT activation downstream of receptor engagement (PMID:10585430, PMID:20484391). Mechanistically, it binds tyrosine-phosphorylated membrane-distal residues of the growth hormone receptor cytoplasmic domain to block STAT5b signaling, a mode distinct from the JAK-directed or membrane-proximal actions of other SOCS family members (PMID:10585430). The same feedback logic operates across diverse cytokine inputs: CISH is induced by IL-2 to limit IL-2-mediated immune responses (PMID:20484391), by IL-13 via STAT6 to restrain CCL26/eotaxin-3 production in lung fibroblasts (PMID:30197185), and constrains STAT3 activity in oral squamous carcinoma cells, where its loss (driven by miR-944) promotes inflammatory cytokine secretion and invasion (PMID:32961483). In immune-cell physiology, CISH sets activation thresholds: it negatively regulates both IL-15 and natural cytotoxicity receptor (NCR) signaling in NK cells, and its deletion lowers activation thresholds, reduces TIGIT-associated exhaustion, and enhances antitumor cytotoxicity (PMID:35589278), while during dendritic-cell development it brakes STAT5-driven progenitor proliferation to permit differentiation (PMID:22002016). Beyond cytokine feedback, CISH also acts as a substrate-targeting adaptor for proteasomal degradation: in activated T cells from older adults it targets the V-ATPase subunit ATP6V1A for degradation, impairing lysosomal function and driving export of mitochondrial DNA that contributes to inflammaging (PMID:37118554).

1. 1999 Medium

   Established the molecular mechanism by which CISH inhibits cytokine signaling, distinguishing it from other SOCS proteins by showing it engages phosphorylated receptor tyrosines rather than the kinase directly.

   Evidence GST pulldown with tyrosine-phosphorylated GHR fusion proteins and STAT5b reporter assays in COS cells

   PMID:10585430

   Open questions at the time

   • Single in vitro binding study; no structural model of the SH2-phosphotyrosine interaction
   • Whether CIS recruits a degradation machinery to GHR not addressed here
2. 2010 Medium

   Connected CISH function to IL-2-driven immune signaling in humans by showing promoter variants blunt IL-2-induced CISH expression, implicating it as a tunable feedback node in primary cells.

   Evidence Case-control genetic association with functional measurement of CISH induction in PBMCs from variant vs wild-type carriers after IL-2 stimulation

   PMID:20484391

   Open questions at the time

   • Downstream signaling consequences of reduced CISH not mechanistically dissected
   • Does not identify which receptor tyrosines CISH engages in the IL-2 context
3. 2011 Medium

   Defined a developmental role for CISH as a STAT5 brake during dendritic-cell maturation, showing the feedback inhibitor also shapes immune-cell differentiation rather than only acute signaling.

   Evidence siRNA knockdown in mouse bone marrow-derived DCs with proliferation, cytokine, surface-marker readouts and in vivo tumor immunotherapy models

   PMID:22002016

   Open questions at the time

   • Knockdown only; not validated in conditional knockout
   • Direct receptor target in DC progenitors not identified
4. 2018 Medium

   Extended the STAT-feedback model to IL-13/STAT6 signaling, showing CISH restrains an allergic-inflammation chemokine output in a non-immune stromal cell type.

   Evidence Reciprocal siRNA knockdown and overexpression in human lung fibroblasts with CCL26 readout and STAT6 phospho-blotting

   PMID:30197185

   Open questions at the time

   • Mechanism of CISH action on the IL-13 receptor not mapped
   • Single cell type, single lab
5. 2020 Medium

   Showed CISH is a tumor-suppressive STAT3 brake whose loss via miR-944 drives oncogenic signaling, generalizing its feedback role to STAT3 and to cancer biology.

   Evidence Luciferase reporter target validation plus reciprocal gain/loss-of-function with STAT3 phospho-blotting and invasion assays in oral squamous carcinoma cells

   PMID:32961483

   Open questions at the time

   • Direct biochemical link between CISH and STAT3 not resolved
   • In vitro cell-line evidence only
6. 2022 High

   Identified CISH as a regulator of NCR signaling beyond IL-15 in NK cells and validated it as an immunotherapy target by showing deletion enhances cytotoxicity and limits exhaustion.

   Evidence NK-specific conditional Cish-knockout mouse with in vitro signaling/cytotoxicity assays, in vivo tumor models, and orthogonal CRISPRi in human NK cells

   PMID:35589278

   Open questions at the time

   • Precise NCR receptor phosphotyrosines bound by CISH not mapped
   • Mechanism linking CISH loss to reduced TIGIT not defined
7. 2023 High

   Revealed a non-canonical CISH function as a substrate-targeting adaptor driving ATP6V1A degradation, linking CISH to lysosomal failure and mtDNA-driven inflammaging in aged T cells.

   Evidence CISH silencing in primary human T cells from older adults with ATP6V1A blotting, lysosomal/amphisome imaging, extracellular mtDNA measurement, and in vivo CD4+ T cell responses

   PMID:37118554

   Open questions at the time

   • E3 ligase/proteasomal machinery CISH recruits to ATP6V1A not identified
   • Whether SH2 phosphotyrosine binding mediates ATP6V1A targeting unknown

• How CISH selects between its phosphotyrosine-receptor feedback role and its substrate-degradation adaptor role, and the structural basis and ubiquitin machinery underlying ATP6V1A targeting, remain unresolved.
• No structural model of CISH bound to any receptor or substrate in the corpus
• Identity of the ubiquitin ligase partner not established
• Determinants of substrate vs receptor selectivity unknown