Basic fibroblast growth factor-induced translocation of p21-activated kinase to the membrane is independent of phospholipase C-γ1 in the differentiation of PC12 cells

Abstract

Abstractp21-activated kinase (PAK) targeting to the plasma membrane is essential for PC12 cell neurite outgrowth. Phospholipase C-γ γ γ γ1 (PLC-γ γ γ γ1) can mediate the PAK translocation in response to growth factors, since PLC-γ γ γ γ1 binds to both tyrosine-phosphorylated receptor tyrosine kinases and PAK through its SH2 and SH3 domain, respectively. In the present study, we examined a potential role for PLC-γ γ γ γ1 in the basic fibroblast growth factor (bFGF)-induced PAK translocation using stable PC12 cell lines that overexpress in a tetracycline-inducible manner either the wild-type FGFR-1 or the Y766F FGFR-1 mutant. Phosphatidylinositol hydrolysis was increased 6.5-fold in response to bFGF in the wild type cells but negligible in the mutant cells. The recombinant GST-PLC-γ γ γ γ1 SH3 was able to bind to PAK1 but not GST alone. However, examination of PLC-γ γ γ γ1 as an adaptor for translocation of PAK1 in cells showed that both cells transfected with pEGFP-PAK1 was able to differentiate for 24 h, as visualized by laser confocal microscopy. Translocation of PAK1 to growth cones occurs at similar levels in both wild and mutant cells. These results suggest that a protein(s) other than PLC-γ γ γ γ1 is functionally relevant for PAK targeting.

Gastrointestinal hormones/neurotransmitters and growth factors can activate P21 activated kinase 2 in pancreatic acinar cells by novel mechanisms

“…Also, in epidermal cells EGF activated PAK2[25] as well as stimulating PAK1 in Cos7 cells[26]. Similarly, in PC-12 cells[27–29] bFGF stimulated cell growth by activating PAK1/PAK2. These results demonstrate that growth factors´ ability to activate Group-I-PAKs can vary markedly in different cells.…”

“…PAK3 has a much more restricted expression, being predominantly expressed in the brain, although recent reports has identify it in enteroendocrine cells [17]. Studies demonstrate that PAKs play an important signaling role in various tissues for a wide range of cellular stimuli including bioactive lipids [18,19], oncogenes [20], chemokines [21], growth factors [22–29], cellular stress [9,10], radiation [30], and with activation of some G-protein-coupled receptors [26,31]. However, there is little information on the activation of Group-I-PAKs by gastrointestinal (GI) hormones/neurotransmitters and GI growth factors in normal GI tissues.…”