Activation of p38 Mitogen-activated Protein Kinase by PYK2/Related Adhesion Focal Tyrosine Kinase-dependent Mechanism

Abstract

The stress-activated p38 mitogen-activated protein kinase (p38 MAPK), a member of the subgroup of mammalian kinases, appears to play an important role in regulating inflammatory responses, including cytokine secretion and apoptosis. The upstream mediators that link extracellular signals with the p38 MAPK signaling pathway are currently unknown. Here we demonstrate that pp125 focal adhesion kinase-related tyrosine kinase RAFTK (also known as PYK2, CADTK) is activated specifically by methylmethane sulfonate (MMS) and hyperosmolarity but not by ultraviolet radiation, ionizing radiation, or cis-platinum. Overexpression of RAFTK leads to the activation of p38 MAPK. Furthermore, overexpression of a dominant-negative mutant of RAFTK (RAFTK K-M) inhibits MMS-induced p38 MAPK activation. MKK3 and MKK6 are known potential constituents of p38 MAPK signaling pathway, whereas SEK1 and MEK1 are upstream activators of SAPK/JNK and ERK pathways, respectively. We observe that the dominantnegative mutant of MKK3 but not of MKK6, SEK1, or MEK1 inhibits RAFTK-induced p38 MAPK activity. Furthermore, the results demonstrate that treatment of cells with 1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid, tetra(acetoxymethyl)-ester, a membranepermeable calcium chelator, inhibits MMS-induced activation of RAFTK and p38 MAPK. Taken together, these findings indicate that RAFTK represents a stress-sensitive mediator of the p38 MAPK signaling pathway in response to certain cytotoxic agents.The mitogen-activated protein kinases (MAPKs) 1 are induced in response to diverse classes of inducers in the transduction of signals from the cell membrane to the nucleus. MAPKs are proline-directed Ser/Thr protein kinases that are regulated by extracellular signals including growth factors and cellular stress (1-3). The well characterized MAPK subfamily includes ERK1 and ERK2, which are activated by growth factors via the conserved Ras/Raf/MEK pathway (4 -7).c-Jun N-terminal protein kinases (JNKs) or stress-activated protein kinases (SAPKs) represent a second class of the mammalian MAPKs, which are primarily activated in response to tumor necrosis factor, interleukin-1, UV-, and DNA-damaging agents (5, 8 -11). A recently identified novel protein tyrosine kinase, related adhesion focal tyrosine kinase (RAFTK) (12) (also known as Pyk2, Refs. 13 and 14); CADTK, Ref. 15) has been shown to be involved upstream to ERKs and JNK signaling pathways (14,16). RAFTK is also a close relative to pp125 FAK tyrosine kinase and is activated by various extracellular signals that increase intracellular calcium concentrations (13). Moreover, RAFTK can tyrosine phosphorylate and modulate the action of ion channels and appears to function as an intermediate that links various calcium signals with both short-and long-term responses in neuronal cells (13).An additional class, which presents substantial similarity to the Saccharomyces cerevisiae HOG1 kinase involved in response to increased extracellular osmolarity (17), is p38 MAPK. p38 MAPK can also be activated by chan...

Cardiomyocyte Apoptosis Triggered by RAFTK/pyk2 via Src Kinase Is Antagonized by Paxillin

“…Tumor necrosis factor ␣-mediated activation of JNK leading to apoptosis in human neutrophils is decreased by inhibition of RAFTK/pyk2 (47). RAFTK/ pyk2 also mediates apoptotic signaling via p38 activity in nonmyocyte cells (48,49). In fact, apoptosis mediated by p38 is blocked by overexpression of dominant negative RAFTK/pyk2 (49).…”

ErbB-2 via PYK2 upregulates the adhesive ability of androgen receptor-positive human prostate cancer cells

“…Additionally, LNCaP cells express an inactive form of FAK (Tremblay et al, 1996). PYK2-mediated functions are carried out by activating multiple downstream signaling molecules, including ERK/ MAPK (Lev et al, 1995), p38/MAPK (Pandey et al, 1999), c-Src (Dikic et al, 1996) and paxillin (Li and Earp, 1997), which lead to the differential regulation of cell adhesion in different cell types. While elevated ERK/MAPK, p38/MAPK and c-Src activities are correlated with increased PYK2 activity and enhanced adhesion in C-81 as well as PYK2 cDNA-transfected C-33 cells (Supplementary Figure 1A and 2), only ERK/ MAPK activity was consistently reduced by expressing the Y402F or the K457A-PYK2 mutants in C-81 cells, correlated with a decreased adhesion (Figure 6, Supplementary Figure 1B).…”

Variations of Proline-Rich Kinase Pyk2 Expression Correlate with Prostate Cancer Progression

“…Despite large efforts and several candidate genes, there is not yet a definite correlation between mutation or alteration in the expression of genes involved in the apoptotic process with different stages of prostate cancer progression (Bostwick et al, 2000;Moul, 1999). However, current studies on the relation of Pyk2 expression to apoptosis assign Pyk2 a role in the pathway that induces apoptosis (Chauhan et al, 1999;Pandey et al, 1999aPandey et al, , 1999bSusa 1999). Xiong and Parson (1997) report that the ectopic expression of Pyk2 causes apoptosis in several fibroblast and epithelial cell lines and that loss of Pyk2 can cause resistance to physiologic apoptosis.…”