Src family protein tyrosine kinases

Parson, IT, and Parson, S.J. Src family protein tyrosine kinases cooperating with growth factor and adhesion signaling pathways (1997) Curr. Op. Cell Biol. 9, 187-192... 

Parsons JT, Parsons SJ. Src family protein tyrosine kinases 64. 

Sieg DJ, liic D, Jones KC, Damsky CH, Hunter T, Schlaepfer DD. Pyk2 and Src-family protein-tyrosine kinases compensate for the loss of FAK in fibronectin-stimulated signaling events but Pyk2 does not fiilly function to enhance FAK- cell migration. EMBO J 1998 17 5933-5947. 

Schlaepfer, D. D., and T. Hunter. 1996. Evidence for in vivo phosphorylation of the Grb2 SH2-domain binding site on focal adhesion kinase by Src-family protein-tyrosine kinases. Mol Cell Biol 16(10) 5623-33. 

Figure 13.32 Regulation of the catalytic activity of members of the Src family of tyrosine kinases, (a) The inactive form based on structure determinations. Helix aC is in a position and orientation where the catalytically important Glu residue is facing away from the active site. The activation segment has a conformation that through steric contacts blocks the catalytically competent positioning of helix aC. (b) A hypothetical active conformation based on comparisons with the active forms of other similar protein kinases. The linker region is released from SH3, and the activation segment changes its structure to allow helix aC to move and bring the Glu residue into the active site in contact with an important Lys residue.

Like all immunoreceptor family members, FceRI lacks intrinsic tyrosine kinase activity. IgE and antigen-induced crosshnking of FceRI initiates a complex series of phosphate transfer events via the activation of non-receptor Src, Syk and Tec family protein tyrosine kinases (fig. 1). The Src family kinase Lyn, which associates with the FceRI p subunit in mast cells, transphosphorylates neighboring FceRI ITAMs after receptor aggregation [7, 26]. Once phosphorylated, the p chain ITAM binds to the SH2 domain of additional Lyn molecules, while the phosphorylated y chain ITAM recruits Syk to the receptor complex, where it is activated by both autophosphorylation and phosphorylation by Lyn [2, 7,15, 26]. 

The Src homology 3 (SH3) domain of a-spectrin was the first SH3 domain structure to be solved (Musacchio et al., 1992). The domain was initially identified as regions of similar sequence found within signaling proteins, such as the Src family of tyrosine kinases, the Crk adaptor... 

S ATP -I- protein <139, 140, 167, 168> (<139>, phosphorylates the regulatory C-terminal tyrosine residue present on cytoplasmic tyrosine kinases of the Src family [383] <140>, CSK phosphorylates other members of the src-family of tyrosine kinases at their regulatory carboxy-terminus [385] <167>, phosphorylates and inactivates the actin binding/depolymerizing factor cofilin and induces actin cytoskeletal changes [441] <168>, GST-Limkl-fusion protein can autophosphorylate on serine, tyrosine and threonine residues in vitro [448]) (Reversibility <139, 140, 167, 168> [383, 385, 441, 448]) [383, 385, 441, 448]... 

S ATP -I- protein <140> (<140>, CSK phosphorylates other members of the src-family of tyrosine kinases at their regulatory carboxy-terminus. By regulating the activity of these kinases, CSK may play an important role in cell growth and development [385]) (Reversibility <140> [385]) [385]... 

In spite of having no intrinsic catalytic domains, activation of T lymphocytes commences with tyrosine phosphorylations, activation of PLC-v with production of IP3 and DAG, and elevation of cytosolic free Ca2+. Thus, the consequences of receptor ligation are not dissimilar from those induced by the receptors for EGF or PDGF. An early study trying to explain the induction of tyrosine kinase activity resulted in the discovery of the nonreceptor protein tyrosine kinase Lck (p56lck), a T-cell-specific member of the Src family. Lck is associated with the cytosolic tail of CD4 (in helper T cells) or CD8 (in cytotoxic T cells) (Figure 8.14). As mentioned, the extracellular domains of these... 

Nonreceptor protein tyrosine kinases contain a catalytic domain, as well as various regulatory domains important for proper functioning of the enzyme. NRPTKs are found in the inner leaflet of the plasma membrane, cytosol, endosomal membranes and nucleus. These include the Src, Jak, Abl, Tec, Ack, Csk, Fak, Fes, Frk and Syk subfamilies (Fig. 24-3). Since a great deal is known about the structure and regulation of the Src family tyrosine kinase, we will use it to illustrate the principles in NRPTK signaling unique features in other subfamilies will be indicated... 

Src is the prototype of the superfamily of protein tyrosine kinases and was one of the first protein kinases to be characterized by various genetic, cellular, and structure-function studies to help imderstand its role in signal transduction pathways as well as in disease processes, including cancer, osteoporosis, and both tumor- and inflammation-mediated bone loss [28-38]. In fact, studies on Src provided some of the first evidence correlating protein kinase activity and substrate protein phosphorylation in the regulation of signal transduction pathways relative to normal cellular activity as well as mahgnant transformations. Src family kinases include Fyn, Yes, Yrk, Blk, Fgr, Hck, Lyn,... 

N-Myristoylation is achieved by the covalent attachment of the 14-carbon saturated myristic acid (C14 0) to the N-terminal glycine residue of various proteins with formation of an irreversible amide bond (Table l). 10 This process is cotranslational and is catalyzed by a monomeric enzyme called jV-myri s toy 11ransferase. 24 Several proteins of diverse families, including tyrosine kinases of the Src family, the alanine-rich C kinase substrate (MARKS), the HIV Nef phosphoprotein, and the a-subunit of heterotrimeric G protein, carry a myr-istoylated N-terminal glycine residue which in some cases is in close proximity to a site that can be S-acylated with a fatty acid. Functional studies of these proteins have shown an important structural role for the myristoyl chain not only in terms of enhanced membrane affinity of the proteins, but also of stabilization of their three-dimensional structure in the cytosolic form. Once exposed, the myristoyl chain promotes membrane association of the protein. 5 The myristoyl moiety however, is not sufficiently hydrophobic to anchor the protein to the membrane permanently, 25,26 and in vivo this interaction is further modulated by a variety of switches that operate through covalent or noncovalent modifications of the protein. 4,5,27 In MARKS, for example, multiple phosphorylation of a positively charged domain moves the protein back to the cytosolic compartment due to the mutated electrostatic properties of the protein, a so-called myristoyl-electrostatic switch. 28 ... 

Myristoylation is generally considered a constitutive process and a permanent modification. As shown above the myristoic anchor may function as a switch during regulated membrane anchoring. Examples for myristoylated proteins are the cytoplasmic protein tyrosine kinases (family of the Src-kinases, chapter 8), as well as the a-subunit of the heterotrim eric G-proteins (chapter 5). 

Examples of receptor-associated tyrosine kinases are given in Table 8.1. Most of the associated protein tyrosine kinases belong to the family of Src kinases (see 8.3) and the Jak kinases (see 11.1.3). 

In an in vitro model, exposure of lymphoma cells to rituximab resulted in the activation of the Src-family of protein tyrosine kinases (13), leading to the phosphorylation of PLCy2, which induces calcium influx and activates caspase 3, resulting in promotion of apoptotic cell death (8,14). Another in vitro model showed that exposure to rituximab resulted in the sustained phosphorylation of p38-MAPK, JNK, and ERK kinases... 

The Rous sarcoma virus oncogene v-src and a family of related oncogenes are derived from protein tyrosine kinases that are attached with the aid of a... 

Vetrie, D., I. Vorechovsky, P. Sideras, J. Holland, A. Davies, F. Flinter, L. Hammarstrom, C. Kinnon, R. Levinsky, M. Bobrow, and et al. 1993. The gene involved in X-linked agammaglobulinaemia is a member of the src family of protein-tyrosine kinases. Nature 361 226-233. 

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