PKG II reverses HGF-triggered cellular activities by phosphorylating serine 985 of c-Met in gastric cancer cells

Abstract

Previous studies showed that type II cGMP-dependent protein kinase G (PKG II) could inhibit the activation of epidermal growth factor receptor (EGFR). Both c-Met and EGFR belong to family of receptor tyrosine kinases (RTKs) and have high molecular analogy. However, the effect of PKG II on c-Met activation is unclear. This study was designed to investigate the inhibitory effect of PKG II on the activation of c-Met and consequent biological activities. The results from CCK8 assay, Transwell assay and TUNEL assay showed that HGF enhanced cell proliferation and migration, and decreased cell apoptosis. Activated PKG II reversed the above changes caused by HGF. Immunoprecipitation and Western blotting results showed that PKG II could bind with c-Met and phosphorylate its Ser985, and thereby inhibited HGF-induced activation of c-Met and MAPK/ERK and PI3K/Akt/mTOR mediated signal transduction. When Ser985 of c-Met was mutated to Alanine for preventing phosphorylation of this site, the blocking effect of PKG II on c-Met activation was annulled. When Ser985 of c-Met was mutated to Aspartic acid for mimicking phosphorylation of this site, HGF-induced activation of c-Met was prevented. In conclusion, the results indicated that PKG II could block c-Met activation via phosphorylating Ser985 of this RTK.

PKG II inhibits PDGF‐BB triggered biological activities by phosphorylating PDGFRβ in gastric cancer cells

“…In previous research, we have verified that PKG II inhibited EGFR, HGFR, and VEGFR through similar mechanism: PKG II decreased the activation of the these RTKs by phosphorylating their serine/threonine residues (Jiang et al, 2013a;Wang et al, 2016a;Wu et al, 2016). However, whether PKG II inhibited the activation of PDGFRb and the detailed mechanism of the inhibition has not yet been elucidated until now.…”

“…Emerging evidence suggests that PKG II, a classical protein kinase, can exert antineoplastic activity in different cancers, indicating its role as a potential anti-tumor factor (Swartling et al, 2009;Karami-Tehrani et al, 2012). In previous research we reported that PKG II could inhibit the phosphorylation/activation of several RTKs, including EGFR, HGFR, VEGFR, and IGF-1R, and the important downstream signal molecules in gastric cancer cells (Jiang al., 2013a, 2013bWu et al, 2016). PDGFRb also belongs to RTK family and shares similar molecular conformation with the other RTKs.…”

“…Serial reports have demonstrated that PKG II inhibited EGF‐EGFR related MAPK/JNK, MAPK/ERK, and PI3K/AKT mediated signal transduction pathways, resulting from the impediment of EGFR activation in gastric cancer cell lines (Lan et al, ; Wu et al, ; Jiang et al, ; Wu et al, ). In addition, PKG II also effectively inhibited the phosphorylation/activation of other RTK, such as vascular endothelial growth factor receptor (VEGFR) and c‐Met (Wang et al, ; Wu et al, ). Because of the high conservation of RTKs in molecular structure, we speculated that PKG II may also have a similar inhibitory effect on platelet‐derived growth factor receptor (PDGFR).…”

Histone acetyltransferase p300/CBP inhibitor C646 blocks the survival and invasion pathways of gastric cancer cell lines

“…According to previous studies, the tumourigenesis and development of GC were closely related to the receptor tyrosine kinase (RTK) c-Met (24)(25)(26). The activation of c-Met triggers signal transduction through the MAPK or PI3K/Akt/mTOR signalling pathways, which initiates cell proliferation and migration, regulates the cell cycle and reduces cell apoptosis (24). Erk 1/2 and Akt are key members of the MAPK and PI3K/Akt/mTOR signal pathways, respectively.…”

Hepatocyte growth factor in physiology and infectious diseases

“…The phosphorylation of Ser985 in the juxtamembrane domain also regulates Met activation. Ser985 is phosphorylated either by protein kinase-C (PKC) or type II cGMPdependent protein kinase G (PKG II), and when Ser985 is phosphorylated, HGF-dependent Met tyrosine phosphorylation and subsequent biological responses are suppressed [64][65][66].…”