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ABSTRACT
Natural killer (NK) cells are essential for killing transformed and virally infected cells. To prevent auto-reactivity, NK cell activation is inhibited by inhibitory receptors that activate the tyrosine phosphatase SHP-1, which dephosphorylates signaling molecules crucial for NK cell activation. Initially, only a single SHP-1 substrate was identified in NK cells, the GEF VAV1. We recently demonstrated that under inhibitory conditions, LAT, PLCγ1 and PLCγ2 serve as novel SHP-1 substrates in NK cells. Furthermore, we showed that during NK cell inhibition, LAT is ubiquitylated by c-Cbl and Cbl-b, leading to its proteasomal degradation, abolishing NK cell cytotoxicity. Here, we address the mechanism through which the Cbl proteins are activated following inhibitory receptor engagement. We demonstrate that during NK cell inhibition, the expression level of the Cbl proteins significantly increases. These data suggest that inhibitory KIR receptors regulate the stability of the Cbl proteins, thereby enabling Cbl-mediated inhibition of NK cell cytotoxicity.
Abbreviations
| Cbl | = | Casitas-B-lineage lymphoma |
| CD3 | = | Cluster of differentiation 3 |
| DAG | = | Diacylglycerol |
| GEF | = | Guanine nucleotide exchange factor |
| IP3 | = | Inositoltriphosphate |
| KIR | = | Killer-cell immunoglobulin-like receptor |
| LAT | = | Linker for activation of T cells |
| MHC | = | Major histocompatibility complex |
| NK | = | Natural killer |
| NKIS | = | Natural killer immunological synapse |
| PIP2 | = | Phosphatidylinositol 4,5-bisphosphate |
| PLCγ | = | phospholipase Cγ |
| SHP-1 | = | SH2-domain-containing protein tyrosine phosphatase-1 |
| TCR | = | T-cell receptor |
Disclosure of potential conflicts of interest
No potential conflicts of interest were disclosed.
Funding
This research was funded by the Israel Science Foundation grants no. 1503/08 and 747/13, grant no. 3-10151 from the Chief Scientist Office of the Ministry of Health, and a Taubenblatt Family Foundation Bio-Medicine excellence grant.