|
Tyrosine-protein kinase Lyn is a protein that in humans is encoded in humans by the ''LYN'' gene. Lyn is a member of the Src family of protein tyrosine kinases, which is mainly expressed in hematopoietic cells, in neural tissues liver, and adipose tissue. In various hematopoietic cells, Lyn has emerged as a key enzyme involved in the regulation of cell activation. In these cells, a small amount of LYN is associated with cell surface receptor proteins, including the B cell antigen receptor (BCR), CD40, or CD19.〔Campbell 1999〕 The abbreviation Lyn is derived from Lck/Yes novel tyrosine kinase, Lck and Yes also being members of the Src kinase family. == Function == Lyn has been described to have an inhibitory role in myeloid lineage proliferation. Following engagement of the B cell receptors, Lyn undergoes rapid phosphorylation and activation. LYN activation triggers a cascade of signaling events mediated by Lyn phosphorylation of tyrosine residues within the immunoreceptor tyrosine-based activation motifs (ITAM) of the receptor proteins, and subsequent recruitment and activation of other kinases including Syk, phosholipase Cγ2 (PLCγ2) and phosphatidyl inositol-3 kinase.〔 These kinases provide activation signals, which play critical roles in proliferation, Ca2+ mobilization and cell differentiation. Lyn plays an essential role in the transmission of inhibitory signals through phosphorylation of tyrosine residues within the immunoreceptor tyrosine-based inhibitory motifs (ITIM) in regulatory proteins such as CD22, PIR-B and FCγRIIb1. Their ITIM phosphorylation subsequently leads to recruitment and activation of phosphatases such as SHIP-1 and SHP-1, which further downmodulate signaling pathways, attenuate cell activation and can mediate tolerance. In B cells, Lyn sets the threshold of cell signaling and maintains the balance between activation and inhibition. Lyn thus functions as a rheostat that modulates signaling rather than as a binary on-off switch. Lyn has also been implicated to have a role in the insulin signaling pathway. Activated Lyn phosphorylates insulin receptor substrate 1 (IRS1). This phosphorylation of IRS1 leads to an increase in translocation of Glut-4 to the cell membrane and increased glucose utilization. In turn, activation of the insulin receptor has been shown to increase autophosphorylation of Lyn suggesting a possible feedback loop. The insulin secretagogue, glimepiride (Amaryl®) activates Lyn in adipocytes via the disruption of lipid rafts. This indirect Lyn activation may modulate the extrapancreatic glycemic control activity of glimepiride.〔 Tolimidone is a small molecule lyn activator that is currently under Phase 2a investigation for Type II diabetes.〔(【引用サイトリンク】url=http://www.businesswire.com/news/home/20150303005277/en/Melior-Pharmaceuticals-Initiates-Phase-2-Study-MLR-1023#.VVy7eGCKKkJ )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「LYN」の詳細全文を読む スポンサード リンク
|