ID:KSYK_HUMAN DESCRIPTION: RecName: Full=Tyrosine-protein kinase SYK; EC=2.7.10.2; AltName: Full=Spleen tyrosine kinase; AltName: Full=p72-Syk; FUNCTION: Non-receptor tyrosine kinase which mediates signal transduction downstream of a variety of transmembrane receptors including classical immunoreceptors like the B-cell receptor (BCR). Regulates several biological processes including innate and adaptive immunity, cell adhesion, osteoclast maturation, platelet activation and vascular development. Assembles into signaling complexes with activated receptors at the plasma membrane via interaction between its SH2 domains and the receptor tyrosine- phosphorylated ITAM domains. The association with the receptor can also be indirect and mediated by adapter proteins containing ITAM or partial hemITAM domains. The phosphorylation of the ITAM domains is generally mediated by SRC subfamily kinases upon engagement of the receptor. More rarely signal transduction via SYK could be ITAM-independent. Direct downstream effectors phosphorylated by SYK include VAV1, PLCG1, PI-3-kinase, LCP2 and BLNK. Initially identified as essential in B-cell receptor (BCR) signaling, it is necessary for the maturation of B-cells most probably at the pro-B to pre-B transition. Activated upon BCR engagement, it phosphorylates and activates BLNK an adapter linking the activated BCR to downstream signaling adapters and effectors. It also phosphorylates and activates PLCG1 and the PKC signaling pathway. It also phosphorylates BTK and regulates its activity in B-cell antigen receptor (BCR)-coupled signaling. Beside its function downstream of BCR plays also a role in T-cell receptor signaling. Plays also a crucial role in the innate immune response to fungal, bacterial and viral pathogens. It is for instance activated by the membrane lectin CLEC7A. Upon stimulation by fungal proteins, CLEC7A together with SYK activates immune cells inducing the production of ROS. Also activates the inflammasome and NF-kappa-B-mediated transcription of chemokines and cytokines in presence of pathogens. Regulates neutrophil degranulation and phagocytosis through activation of the MAPK signaling cascade. Also mediates the activation of dendritic cells by cell necrosis stimuli. Also involved in mast cells activation. Also functions downstream of receptors mediating cell adhesion. Relays for instance, integrin-mediated neutrophils and macrophages activation and P-selectin receptor/SELPG-mediated recruitment of leukocytes to inflammatory loci. Plays also a role in non-immune processes. It is for instance involved in vascular development where it may regulate blood and lymphatic vascular separation. It is also required for osteoclast development and function. Functions in the activation of platelets by collagen, mediating PLCG2 phosphorylation and activation. May be coupled to the collagen receptor by the ITAM domain-containing FCER1G. Also activated by the membrane lectin CLEC1B that is required for activation of platelets by PDPN/podoplanin. Involved in platelet adhesion being activated by ITGB3 engaged by fibrinogen. CATALYTIC ACTIVITY: ATP + a [protein]-L-tyrosine = ADP + a [protein]-L-tyrosine phosphate. ENZYME REGULATION: Autoinhibited. Intramolecular binding of the interdomains A and B (also called linker region) to parts of the catalytic domain keep the catalytic center in an inactive conformation. The phosphorylation of the interdomains or the binding of the SH2 domains with dually phosphorylated ITAM domains on transmembrane proteins disrupt those intramolecular interactions allowing the kinase domain to adopt an active conformation. The phosphorylation of SYK and of the ITAM domains which is responsible for SYK activation is essentially mediated by SRC subfamily kinases, like LYN, upon transmembrane receptors engagement. May also be negatively regulated by PTPN6 through dephosphorylation. Downstream signaling adapters and intermediates like BLNK or RHOH may mediate positive and/or negative feedback regulation. Negatively regulated by CBL and CBLB through ubiquitination and probable degradation. Phosphorylates SH3BP2 which in turn may regulate SYK through LYN (By similarity). SUBUNIT: Interacts with LYN; phosphorylates SYK (By similarity). Interacts with RHOH (phosphorylated); regulates mast cells activation (By similarity). Interacts with NFAM1 (phosphorylated); probably involved in BCR signaling (By similarity). Interacts with VAV1 (via SH2 domain); phosphorylates VAV1 upon BCR activation. Interacts with GAB2 (phosphorylated); probably involved in IgE Fc receptor signaling (By similarity). Interacts (via its SH2 domains) with CD79A (via its phosphorylated ITAM domain); the interaction stimulates SYK autophosphorylation and activation (By similarity). Interacts with FCRL3. Interacts (via SH2 domains) with FCER1G (via ITAM domain); activates SYK and mediates neutrophils and macrophages integrin-mediated activation (By similarity). Interacts with ITGB2 and FGR; involved in ITGB2 downstream signaling (By similarity). Interacts with ITGB3; upon activation by ITGB3 promotes platelet adhesion. Interacts (via SH2 domains) with TYROBP (via ITAM domain); involved in neutrophils and macrophages integrin-mediated activation (By similarity). Interacts with MSN and SELPLG; mediates the selectin-dependent activation of SYK by SELPLG. Interacts with BLNK (via SH2 domain). Interacts (via the second SH2 domain) with USP25 (via C-terminus); phosphorylates USP25 and regulates USP25 intracellular levels. Interacts (via SH2 domains) with CLEC1B (dimer). Interacts with CLEC7A; participatex in leukocyte activation in presence of fungal pathogens. Interacts (phosphorylated) with SLA; may regulate SYK through CBL recruitment. Interacts with YWHAG; attenuates BCR- induced membrane translocation and activation of SYK. Interacts with Epstein-Barr virus LMP2A. INTERACTION: P20273:CD22; NbExp=4; IntAct=EBI-78302, EBI-78277; P11049:CD37; NbExp=3; IntAct=EBI-78302, EBI-6139068; SUBCELLULAR LOCATION: Cell membrane (Probable). Cytoplasm, cytosol (Probable). TISSUE SPECIFICITY: Widely expressed in hematopoietic cells (at protein level). Within the B-cells compartment it is for instance expressed for pro-B-cells to plasma cells. DOMAIN: The SH2 domains mediate the interaction of SYK with the phosphorylated ITAM domains of transmembrane proteins. Some proteins like CLEC1B have a partial ITAM domain (also called hemITAM) containing a single YxxL motif. The interaction with SYK requires CLEC1B homodimerization. PTM: Ubiquitinated by CBLB after BCR activation; which promotes proteasomal degradation (By similarity). PTM: Autophosphorylated. Phosphorylated on tyrosine residues by LYN following receptors engagement. Phosphorylation on Tyr-323 creates a binding site for CBL, an adapter protein that serves as a negative regulator of BCR-stimulated calcium ion signaling. Phosphorylation at Tyr-348 creates a binding site for VAV1. Phosphorylation on Tyr-348 and Tyr-352 enhances the phosphorylation and activation of phospholipase C-gamma and the early phase of calcium ion mobilization via a phosphoinositide 3- kinase-independent pathway (By similarity). Phosphorylation on Ser-297 is very common, it peaks 5 minutes after BCR stimulation, and creates a binding site for YWHAG. Phosphorylation at Tyr-630 creates a binding site for BLNK. Dephosphorylated by PTPN6. SIMILARITY: Belongs to the protein kinase superfamily. Tyr protein kinase family. SYK/ZAP-70 subfamily. SIMILARITY: Contains 1 protein kinase domain. SIMILARITY: Contains 2 SH2 domains. WEB RESOURCE: Name=Atlas of Genetics and Cytogenetics in Oncology and Haematology; URL="http://atlasgeneticsoncology.org/Genes/SYKID394.html";
The RNAfold program from the Vienna RNA Package is used to perform the secondary structure predictions and folding calculations. The estimated folding energy is in kcal/mol. The more negative the energy, the more secondary structure the RNA is likely to have.
ModBase Predicted Comparative 3D Structure on P43405
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Orthologous Genes in Other Species
Orthologies between human, mouse, and rat are computed by taking the best BLASTP hit, and filtering out non-syntenic hits. For more distant species reciprocal-best BLASTP hits are used. Note that the absence of an ortholog in the table below may reflect incomplete annotations in the other species rather than a true absence of the orthologous gene.
US Server
Sequence and Links to Tools and Databases 
Common Gene Haplotype Alleles 
