Q06187

FUNCTION: Non-receptor tyrosine kinase indispensable for B lymphocyte development, differentiation and signaling. Binding of antigen to the B-cell antigen receptor (BCR) triggers signaling that ultimately leads to B-cell activation. After BCR engagement and activation at the plasma membrane, phosphorylates PLCG2 at several sites, igniting the downstream signaling pathway through calcium mobilization, followed by activation of the protein kinase C (PKC) family members. PLCG2 phosphorylation is performed in close cooperation with the adapter protein B-cell linker protein BLNK. BTK acts as a platform to bring together a diverse array of signaling proteins and is implicated in cytokine receptor signaling pathways. Plays an important role in the function of immune cells of innate as well as adaptive immunity, as a component of the Toll-like receptors (TLR) pathway. The TLR pathway acts as a primary surveillance system for the detection of pathogens and are crucial to the activation of host defense. Especially, is a critical molecule in regulating TLR9 activation in splenic B-cells. Within the TLR pathway, induces tyrosine phosphorylation of TIRAP which leads to TIRAP degradation. BTK plays also a critical role in transcription regulation. Induces the activity of NF-kappa-B, which is involved in regulating the expression of hundreds of genes. BTK is involved on the signaling pathway linking TLR8 and TLR9 to NF-kappa-B. Transiently phosphorylates transcription factor GTF2I on tyrosine residues in response to BCR. GTF2I then translocates to the nucleus to bind regulatory enhancer elements to modulate gene expression. ARID3A and NFAT are other transcriptional target of BTK. BTK is required for the formation of functional ARID3A DNA-binding complexes. There is however no evidence that BTK itself binds directly to DNA. BTK has a dual role in the regulation of apoptosis. CATALYTIC ACTIVITY: ATP + a [protein]-L-tyrosine = ADP + a [protein]-L-tyrosine phosphate. COFACTOR: Binds 1 zinc ion per subunit. ENZYME REGULATION: Activated by phosphorylation. In primary B lymphocytes, is almost always non-phosphorylated and is thus catalytically inactive. Stimulation of TLR8 and TLR9 causes BTK activation. As a negative feedback mechanism to fine-tune BCR signaling, activated PRKCB down-modulates BTK function via direct phosphorylation of BTK at Ser-180, resulting in translocation of BTK back to the cytoplasmic fraction. PIN1, SH3BP5, and IBTK were also identified as BTK activity inhibitors. Interaction with CAV1 leads to dramatic down-regulation of the kinase activity of BTK. LFM-13A is a specific inhibitor of BTK. Dasatinib, a cancer drug acting as a tyrosine kinase inhibitor, also blocks BTK activity. SUBUNIT: Binds GTF2I through the PH domain. Interacts with SH3BP5 via the SH3 domain. Interacts with IBTK via its PH domain. Interacts with ARID3A, CAV1, FASLG, PIN1, TLR8 and TLR9. SUBCELLULAR LOCATION: Cytoplasm. Cell membrane; Peripheral membrane protein. Nucleus. Note=In steady state, BTK is predominantly cytosolic. Following B-cell receptor (BCR) engagement by antigen, translocates to the plasma membrane through its PH domain. Plasma membrane localization is a critical step in the activation of BTK. A fraction of BTK also shuttles between the nucleus and the cytoplasm, and nuclear export is mediated by the nuclear export receptor CRM1. TISSUE SPECIFICITY: Predominantly expressed in B-lymphocytes. DOMAIN: The PH domain mediates the binding to inositol polyphosphate and phosphoinositides, leading to its targeting to the plasma membrane. It is extended in the BTK kinase family by a region designated the TH (Tec homology) domain, which consists of about 80 residues preceding the SH3 domain. PTM: Following B-cell receptor (BCR) engagement, translocates to the plasma membrane where it gets phosphorylated at Tyr-551 by LYN and SYK. Phosphorylation at Tyr-551 is followed by autophosphorylation of Tyr-223 which may create a docking site for a SH2 containing protein. Phosphorylation at Ser-180 by PRKCB, leads in translocation of BTK back to the cytoplasmic fraction. Phosphorylation at Ser-21 and Ser-115 creates a binding site for PIN1 at these Ser-Pro motifs, and promotes it's recruitment. DISEASE: Defects in BTK are the cause of X-linked agammaglobulinemia (XLA) [MIM:300755]; also known as X-linked agammaglobulinemia type 1 (AGMX1) or immunodeficiency type 1 (IMD1). XLA is a humoral immunodeficiency disease which results in developmental defects in the maturation pathway of B-cells. Affected boys have normal levels of pre-B-cells in their bone marrow but virtually no circulating mature B-lymphocytes. This results in a lack of immunoglobulins of all classes and leads to recurrent bacterial infections like otitis, conjunctivitis, dermatitis, sinusitis in the first few years of life, or even some patients present overwhelming sepsis or meningitis, resulting in death in a few hours. Treatment in most cases is by infusion of intravenous immunoglobulin. DISEASE: Defects in BTK may be the cause of X-linked hypogammaglobulinemia and isolated growth hormone deficiency (XLA- IGHD) [MIM:307200]; also known as agammaglobulinemia and isolated growth hormone deficiency or Fleisher syndrome or isolated growth hormone deficiency type 3 (IGHD3). In rare cases XLA is inherited together with isolated growth hormone deficiency (IGHD). SIMILARITY: Belongs to the protein kinase superfamily. Tyr protein kinase family. TEC subfamily. SIMILARITY: Contains 1 Btk-type zinc finger. SIMILARITY: Contains 1 PH domain. SIMILARITY: Contains 1 protein kinase domain. SIMILARITY: Contains 1 SH2 domain. SIMILARITY: Contains 1 SH3 domain. WEB RESOURCE: Name=Atlas of Genetics and Cytogenetics in Oncology and Haematology; URL="http://atlasgeneticsoncology.org/Genes/BTKID851chXq22.html"; WEB RESOURCE: Name=BTKbase; Note=BTK mutation db; URL="http://bioinf.uta.fi/BTKbase/"; WEB RESOURCE: Name=GeneReviews; URL="http://www.ncbi.nlm.nih.gov/sites/GeneTests/lab/gene/BTK"; GENE SYNONYMS:BTK AGMX1 ATK BPK. COPYRIGHT: Protein annotation is derived from the UniProt Consortium (http://www.uniprot.org/). Distributed under the Creative Commons Attribution-NoDerivs License., SEQUENCE 659 AA; 76281 MW; DF06B5D1FEC257CC CRC64;

BTK_HUMAN

urn:biopax:ModificationFeature:BTK_HUMAN_1, urn:biopax:ModificationFeature:BTK_HUMAN_10, urn:biopax:ModificationFeature:BTK_HUMAN_11, urn:biopax:ModificationFeature:BTK_HUMAN_12, urn:biopax:ModificationFeature:BTK_HUMAN_13, urn:biopax:ModificationFeature:BTK_HUMAN_14, urn:biopax:ModificationFeature:BTK_HUMAN_15, urn:biopax:ModificationFeature:BTK_HUMAN_16, urn:biopax:ModificationFeature:BTK_HUMAN_17, urn:biopax:ModificationFeature:BTK_HUMAN_18, urn:biopax:ModificationFeature:BTK_HUMAN_19, urn:biopax:ModificationFeature:BTK_HUMAN_2, urn:biopax:ModificationFeature:BTK_HUMAN_20, urn:biopax:ModificationFeature:BTK_HUMAN_21, urn:biopax:ModificationFeature:BTK_HUMAN_22, urn:biopax:ModificationFeature:BTK_HUMAN_3, urn:biopax:ModificationFeature:BTK_HUMAN_4, urn:biopax:ModificationFeature:BTK_HUMAN_5, urn:biopax:ModificationFeature:BTK_HUMAN_6, urn:biopax:ModificationFeature:BTK_HUMAN_7, urn:biopax:ModificationFeature:BTK_HUMAN_8, urn:biopax:ModificationFeature:BTK_HUMAN_9

MAAVILESIFLKRSQQKKKTSPLNFKKRLFLLTVHKLSYYEYDFERGRRGSKKGSIDVEKITCVETVVPEKNPPPERQIPRRGEESSEMEQISIIERFPYPFQVVYDEGPLYVFSPTEELRKRWIHQLKNVIRYNSDLVQKYHPCFWIDGQYLCCSQTAKNAMGCQILENRNGSLKPGSSHRKTKKPLPPTPEEDQILKKPLPPEPAAAPVSTSELKKVVALYDYMPMNANDLQLRKGDEYFILEESNLPWWRARDKNGQEGYIPSNYVTEAEDSIEMYEWYSKHMTRSQAEQLLKQEGKEGGFIVRDSSKAGKYTVSVFAKSTGDPQGVIRHYVVCSTPQSQYYLAEKHLFSTIPELINYHQHNSAGLISRLKYPVSQQNKNAPSTAGLGYGSWEIDPKDLTFLKELGTGQFGVVKYGKWRGQYDVAIKMIKEGSMSEDEFIEEAKVMMNLSHEKLVQLYGVCTKQRPIFIITEYMANGCLLNYLREMRHRFQTQQLLEMCKDVCEAMEYLESKQFLHRDLAARNCLVNDQGVVKVSDFGLSRYVLDDEYTSSVGSKFPVRWSPPEVLMYSKFSSKSDIWAFGVLMWEIYSLGKMPYERFTNSETAEHIAQGLRLYRPHLASEKVYTIMYSCWHEKADERPTFKILLSNILDVMDEES