Article

Reciprocal regulation of Abl and receptor tyrosine kinases.

Department of Molecular and Biomedical Pharmacology, University of Kentucky School of Medicine, 800 Rose Street, Lexington, KY 40346, USA.
Cellular signalling (impact factor: 4.09). 04/2009; 21(7):1143-50. DOI:10.1016/j.cellsig.2009.03.003
Source: PubMed

ABSTRACT Previously, we showed that Abl kinases (c-Abl, Arg) are activated downstream of PDGF in a manner dependent on Src kinases and PLC-gamma1, and promote PDGF-mediated proliferation and migration of fibroblasts. We additionally demonstrated that Abl kinases bind directly to PDGFR-beta via their SH2 domains.In this study, we extend these findings by demonstrating that Abl kinases also are activated downstream of aPDGF autocrine growth loop in glioblastoma cells, indicating that the PDGFR-Abl signaling pathway also is likely to be important in glioblastoma development and/or progression.We recently showed that Abl kinases are highly active in many breast cancer cell lines, and the Her-2 receptor tyrosine kinase contributes to c-Abl and Arg kinase activation. In this study, we show that Abl kinase SH2 domains bind directly to Her-2, and like PDGFR-beta , Her-2 directly phosphorylates c-Abl. Previously, we demonstrated that PDGFR-beta directly phosphorylates Abl kinases in vitro, and Abl kinases reciprocally phosphorylate PDGFR-beta . Here, we show that PDGFR-beta-phosphorylation of Abl kinases has functional consequences as PDGFR-beta phosphorylates Abl kinases on Y245 and Y412, sites known to be required for activation of Abl kinases. Moreover, PDGFR-beta phosphorylates Arg on two additional unique sites whose function is unknown. Importantly, we also show that Abl-dependent phosphorylation of PDGFR-beta has functional and biological significances. c-Abl phosphorylates three tyrosine residues on PDGFR-beta (Y686, Y934, Y970), while Arg only phosphorylatesY686. Y686 and Y934 reside in PDGFR-beta catalytic domains, while Y970 is in the C-terminal tail. Using site-directed mutagenesis, we show that Abl-dependent phosphorylation of PDGFR-beta activates PDGFR-beta activity, in vitro, but serves to downregulate PDGFR-mediated chemotaxis. These data are exciting as they indicate that Abl kinases not only are activated by PDGFR and promote PDGFR-mediated proliferation and migration,but also act in an intricate negative feedback loop to turn-off PDGFR-mediated chemotaxis.

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Keywords

Abl kinase SH2 domains bind
 
Abl kinases bind
 
Abl kinases reciprocally phosphorylate PDGFR-beta
 
Abl-dependent phosphorylation
 
aPDGF autocrine growth loop
 
Arg kinase activation
 
breast cancer cell lines
 
C-terminal tail
 
downregulate PDGFR-mediated chemotaxis
 
glioblastoma development
 
intricate negative feedback loop
 
PDGF-mediated proliferation
 
PDGFR-Abl signaling pathway
 
PDGFR-beta activates PDGFR-beta activity
 
PDGFR-beta catalytic domains
 
PDGFR-beta phosphorylates Abl kinases
 
PDGFR-beta phosphorylates Arg
 
PDGFR-mediated proliferation
 
SH2 domains.In
 
turn-off PDGFR-mediated chemotaxis
 

Divyamani Srinivasan