TY - JOUR
T1 - Constitutive diffuse activation of phosphoinositide 3-kinase at the plasma membrane by v-Src suppresses the chemotactic response to PDGF by abrogating the polarity of PDGF receptor signalling
AU - Platek, Anna
AU - Vassilev, Vassil S.
AU - de Diesbach, Philippe
AU - Tyteca, Donatienne
AU - Mettlen, Marcel
AU - Courtoy, Pierre J.
N1 - Funding Information:
We are grateful to Dr. P. Zimmermann as well as to Drs. J.-B. Demoulin and A. Kallin for providing Akt-PH-GFP and HA-tagged hPDGFR β expression vectors, respectively. The secretarial assistance of Mr. Y. Marchand was greatly appreciated. This work was supported by grants (to PJC) from the UCL/FSR, FNRS, Télévie, Actions de Recherches concertées, Région wallonne and IUAP (all from Belgium).
PY - 2007/4/1
Y1 - 2007/4/1
N2 - Cancer cells depend on chemotaxis for invasion and frequently overexpress and/or activate Src. We previously reported that v-Src accelerates motility by promoting phosphoinositide 3-kinase (PI3-K) signalling but abrogates chemotaxis. We here addressed the mechanism of the loss of chemotactic response to platelet-derived growth factor (PDGF) gradients in fibroblasts harbouring a thermosensitive v-Src kinase. At non-permissive temperature, PDGF receptor (PDGFR) signalling, assessed by phosphoY751-specific antibodies (a docking site for PI3-K), was not detected without PDGF and showed a concentration-dependent PDGF response. Both immunolabeling of PI3-K (p110) and live cell imaging of its product (phosphatidylinositol 3,4,5 tris-phosphate) showed PI3-K recruitment and activation at lamellipodia polarized towards a PDGF gradient. Centrosomes and PDGFR- and Src-bearing endosomes were also oriented towards this gradient. Upon v-Src thermoactivation, (i) Y751 phosphorylation was moderately induced without PDGF and synergistically increased with PDGF; (ii) PI3-K was recruited and activated all along the plasma membrane without PDGF and did not polarize in response to a PDGF gradient; and (iii) polarization of centrosomes and of PDGFR-bearing endosomes were also abrogated. Thus, PDGF can further increase PDGFR auto-phosphorylation despite strong Src kinase activity, but diffuse downstream activation of PI3-K by Src abrogates cell polarization and chemotaxis: "signalling requires silence".
AB - Cancer cells depend on chemotaxis for invasion and frequently overexpress and/or activate Src. We previously reported that v-Src accelerates motility by promoting phosphoinositide 3-kinase (PI3-K) signalling but abrogates chemotaxis. We here addressed the mechanism of the loss of chemotactic response to platelet-derived growth factor (PDGF) gradients in fibroblasts harbouring a thermosensitive v-Src kinase. At non-permissive temperature, PDGF receptor (PDGFR) signalling, assessed by phosphoY751-specific antibodies (a docking site for PI3-K), was not detected without PDGF and showed a concentration-dependent PDGF response. Both immunolabeling of PI3-K (p110) and live cell imaging of its product (phosphatidylinositol 3,4,5 tris-phosphate) showed PI3-K recruitment and activation at lamellipodia polarized towards a PDGF gradient. Centrosomes and PDGFR- and Src-bearing endosomes were also oriented towards this gradient. Upon v-Src thermoactivation, (i) Y751 phosphorylation was moderately induced without PDGF and synergistically increased with PDGF; (ii) PI3-K was recruited and activated all along the plasma membrane without PDGF and did not polarize in response to a PDGF gradient; and (iii) polarization of centrosomes and of PDGFR-bearing endosomes were also abrogated. Thus, PDGF can further increase PDGFR auto-phosphorylation despite strong Src kinase activity, but diffuse downstream activation of PI3-K by Src abrogates cell polarization and chemotaxis: "signalling requires silence".
KW - Chemotaxis
KW - Live cell imaging
KW - Phosphoinositide 3-kinase
KW - Platelet-derived growth factor
KW - Src
UR - http://www.scopus.com/inward/record.url?scp=33947304127&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33947304127&partnerID=8YFLogxK
U2 - 10.1016/j.yexcr.2007.01.020
DO - 10.1016/j.yexcr.2007.01.020
M3 - Article
C2 - 17335807
AN - SCOPUS:33947304127
SN - 0014-4827
VL - 313
SP - 1090
EP - 1105
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 6
ER -