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© The Rockefeller University Press,
0021-9525/2000//1269 $5.00
The Journal of Cell Biology, Volume 151, Number 6,
, 2000 1269-1280
Original Article |
Spatial Sensing in Fibroblasts Mediated by 3' Phosphoinositides
tobias.meyer{at}stanford.edu
The directed movement of fibroblasts towards locally released platelet-derived growth factor (PDGF) is a critical event in wound healing. Although recent studies have implicated polarized activation of phosphoinositide (PI) 3-kinase in G protein-mediated chemotaxis, the role of 3' PI lipids in tyrosine kinase-triggered chemotaxis is not well understood. Using evanescent wave microscopy and green fluorescent protein–tagged Akt pleckstrin homology domain (GFP–AktPH) as a molecular sensor, we show that application of a shallow PDGF gradient triggers a markedly steeper gradient in 3' PI lipids in the adhesion zone of fibroblasts. Polar GFP–AktPH gradients, as well as a new type of radial gradient, were measured from front to rear and from the periphery to the center of the adhesion zone, respectively. A strong spatial correlation between polarized 3' PI production and rapid membrane spreading implicates 3' PI lipids as a direct mediator of polarized migration. Analysis of the temporal changes of 3' PI gradients in the adhesion zone revealed a fast diffusion coefficient (0.5 µm2/s) and short lifetime of 3' PIs of <1 min. Together, this study suggests that the tyrosine kinase-coupled directional movement of fibroblasts and their radial membrane activity are controlled by local generation and rapid degradation of 3' PI second messengers.
Key Words: chemotaxis • signal transduction • phosphatidylinositol 3-kinase • receptor protein-tyrosine kinases • platelet-derived growth factor
© 2000 The Rockefeller University Press
The online version of this article contains supplemental material.Mary Teruel's current address is Department of Molecular Pharmacology, 269 Campus Drive, Room 3215, Stanford University Medical Center, Stanford, CA 94305-5174.
Jason M. Haugh's current address is Department of Chemical Engineering, North Carolina State University, Raleigh, NC 27695-7905.
Abbreviations used in this paper: GFP, green fluorescent protein; GFP–AktPH, GFP-conjugated pleckstrin homology domain of Akt; PDGF, platelet-derived growth factor; PH, pleckstrin homology; PI, phosphoinositide.
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