CDB15:0000681 GAS6 — TYRO3
Experimentally validated in Human, Mixed species; Orthology-inferred in Human, Mouse, Rat, Frog, Zebrafish, Chicken, Macaque, Pig, Dog, Cow, Chimp, Horse, Marmoset, Sheep
Title
Journal:; Year Published:
Abstract
Receptor tyrosine kinases, TYRO3, AXL, and MER, demonstrate distinct patterns and complex regulation of ligand-induced activation.
The Journal of biological chemistry, 2014; PubMed, Homo sapiens GAS6 — Homo sapiens TYRO3
ABSTRACT: TYRO3, AXL, and MER receptors (TAMs) are three homologous type I receptor-tyrosine kinases that are activated by endogenous ligands, protein S (PROS1) and growth arrest-specific gene 6 (GAS6). These ligands can either activate TAMs as soluble factors, or, in turn, opsonize phosphatidylserine (PS) on apoptotic cells (ACs) and serve as bridging molecules between ACs and TAMs. Abnormal expression and activation of TAMs have been implicated in promoting proliferation and survival of cancer cells, as well as in suppressing anti-tumor immunity. Despite the fact that TAM receptors share significant similarity, little is known about the specificity of interaction between TAM receptors and their ligands, particularly in the context of ACs, and about the functional diversity of TAM receptors. To study ligand-mediated activation of TAMs, we generated a series of reporter cell lines expressing chimeric TAM receptors. Using this system, we found that each TAM receptor has a unique pattern of interaction with and activation by GAS6 and PROS1, which is also differentially affected by the presence of ACs, PS-containing lipid vesicles and enveloped virus. We also demonstrated that γ-carboxylation of ligands is essential for the full activation of TAMs and that soluble immunoglobulin-like TAM domains act as specific ligand antagonists. These studies demonstrate that, despite their similarity, TYRO3, AXL, and MER are likely to perform distinct functions in both immunoregulation and the recognition and removal of ACs.
Characterization of Gas6, a member of the superfamily of G domain-containing proteins, as a ligand for Rse and Axl.
The Journal of biological chemistry, 1996; PubMed, Homo sapiens GAS6 — Homo sapiens TYRO3
ABSTRACT: Rse, Ax1, and c-Mer comprise a family of cell adhesion molecule-related tyrosine kinase receptors. Human Gas6 was recently shown to act as a ligand for both human Rse (Godowski et al., 1995) and human Ax1 (Varnum et al., 1995). Gas6 contains an NH2-terminal Gla domain followed by four epidermal growth factor-like repeats and tandem globular (G) domains. The G domains are related to those found in sex hormone-binding globulin and to those utilized by laminin and agrin for binding to the dystroglycan complex. A series of Gas6 variants were tested for their ability to bind to Rse and Ax1. The Gla domain and epidermal growth factor-like repeats were not required for receptor binding, as deletion variants of Gas6 which lacked these domains bound to the extracellular domains of both Rse and Axl. A deletion variant of Gas6 containing just the G domain region was shown to activate Rse phosphorylation. These results provide evidence that G domains can act as signaling molecules by activating transmembrane receptor tyrosine kinases. Furthermore, they provide a structural link between the activation of cell adhesion related receptors and the control of cell growth and differentiation by the G domain-containing superfamily of proteins.
Identification of the product of growth arrest-specific gene 6 as a common ligand for Axl, Sky, and Mer receptor tyrosine kinases.
The Journal of biological chemistry, 1996; PubMed, Homo sapiens GAS6 — Homo sapiens TYRO3
ABSTRACT: Axl, Sky, and Mer, members of an Axl/Sky receptor tyrosine kinase subfamily, are typified by the cell adhesion molecule-related extracellular domain. The product of growth arrest-specific gene 6 (Gas6), structurally homologous to the anticoagulant protein S, was recently identified as the ligand for Axl and Sky, but the ligand for Mer remained unknown. We have now obtained evidence that Gas6 can also function as a ligand for Mer. Co-precipitation analysis, using soluble receptors of Axl, Sky, and Mer (Axl-Fc, Sky-Fc, and Mer-Fc) composed of the extracellular domain of receptors fused to the Fc domain of immunoglobulin G1, clearly showed that Gas6, but not protein S, specifically bound to Axl-Fc, Sky-Fc, and Mer-Fc fusion proteins. Quantitative kinetic analyses using a BIAcore biosensor instrument revealed dissociation constants (Kd) of the binding of rat Gas6 to Axl-Fc, Sky-Fc, and Mer-Fc are 0.4, 2.7, and 29 nM, respectively. We also found that Gas6 stimulated tyrosine phosphorylation of Axl, Sky, and Mer receptors ectopically expressed in Chinese hamster ovary cells. Taken together, these findings suggest that Gas6 is a common ligand for Axl, Sky, and Mer, all known members of an Axl/Sky receptor subfamily.