Integrin 
Mediates Chemotactic and Haptotactic Motility in Human Melanoma Cells through Different Signaling Pathways (*)
- From the National Institutes of Health, National Cancer Institute, Laboratory of Pathology, Bethesda, Maryland 20892
- §To whom correspondence should be addressed: National Institutes of Health, National Cancer Institute, Laboratory of Pathology, Bldg. 10, Rm. 2A33, Bethesda, MD 20892. Tel.: 301-496-1843; Fax: 301-480-0853.
Abstract
Distinctions between chemotaxis and haptotaxis of cells to extracellular matrix proteins have not been defined in terms of
mechanisms or signaling pathways. Migration of A2058 human melanoma cells to soluble (chemotaxis) and substratum-bound (haptotaxis)
vitronectin, mediated by α
β
, provided a system with which to address these questions. Both chemotaxis and haptotaxis were completely inhibited by treatment
with RGD-containing peptides. Chemotaxis was abolished by a blocking antibody to α
β
(LM609), whereas haptotaxis was inhibited only by approximately 50%, suggesting involvement of multiple receptors and/or
signaling pathways. However, blocking antibodies to α
β
, also present on A2058 cells, did not inhibit. Pertussis toxin treatment of cells inhibited chemotaxis by >80%, but did not
inhibit haptotaxis. Adhesion and spreading over vitronectin induced the phosphorylation of paxillin on tyrosine. In cells
migrating over substratum-bound vitronectin, tyrosine phosphorylation of paxillin increased 5-fold between 45 min and 5 h.
Dilutions of anti-α
β
that inhibited haptotaxis also inhibited phosphorylation of paxillin (by 
50%) and modestly reduced cell spreading. In contrast, soluble vitronectin (50-100 μg/ml) did not induce tyrosine phosphorylation
of paxillin. The data suggest that soluble vitronectin stimulates chemotaxis predominantly through a G protein-mediated pathway
that is functionally linked to α
β
. Haptotaxis is analogous to directional cell spreading and requires α
β
-mediated tyrosine phosphorylation of paxillin.
Footnotes
-
↵* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- ECM
-
extracellular matrix
- VN
-
vitronectin
- CTX
-
chemotaxis
- HTX
-
haptotaxis
- PT
-
pertussis toxin
- FBS
-
fetal bovine serum
- BSA
-
bovine serum albumin
- PAGE
-
polyacrylamide gel electrophoresis
- Ab
-
antibody
- DMEM
-
Dulbecco's modified Eagle's medium
- DPBS
-
Dulbecco's phosphate-buffered saline
- AEBSF
-
4-(2-aminoethyl)benzenesulfonyl fluoride hydrochlorine.
-
- Received September 13, 1995.
- Revision received November 30, 1995.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
