Type IV collagen stimulates an increase in intracellular calcium. Potential role in tumor cell motility.
Type IV collagen (Coll IV), a component of the extracellular matrix, stimulates motility in the A2058 human melanoma cell line, a response that is inhibited by pertussis toxin (PT). Fibronectin (FN)-induced chemotaxis in this cell line is not affected by PT. To understand the mechanism of cellular signaling, single cell intracellular Ca2+ responses to Coll IV and FN were studied using Fura-2 and digital imaging fluorescence microscopy. Coll IV, at a dose that stimulates motility (100 micrograms/ml, 185 nM), induces a significant rise in cytosolic free Ca2+ concentration ([Ca2+]i) within 100 s. This response is not inhibited by PT. Treatment of the cells with FN 30 micrograms/ml (70 nM), a dose that stimulates near-maximal chemotaxis, does not increase [Ca2+]i appreciably. Removal of extracellular Ca2+ fails to inhibit the Coll IV-stimulated rise in Ca2+ in all cells. Depletion of extracellular Ca2+ and pretreatment of cells with Ca2+ channel blockers only partially inhibits Coll IV-induced motility. Depletion of intracellular Ca2+ inhibits both chemotaxis and the Coll IV-induced increase in intracellular Ca2+. Coll IV does not stimulate membrane phosphoinositide hydrolysis. We conclude that Coll IV treatment induces an inositol 1,4,5-trisphosphate-independent release of intracellular Ca2+ stores which appears to play a necessary role in the chemotactic response of A2058 cells but is not mediated by a PT-sensitive G-protein. This response is not seen in cells exposed to FN, suggesting different intracellular signaling mechanisms for stimulated motility between these two extracellular matrix molecules.
Savarese
D M
DM
Medicine Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
Russell
J T
JT
Fatatis
A
A
Liotta
L A
LA
D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002633:Chemotaxis; D002855:Chromatography, Thin Layer; D003094:Collagen / Q000502:physiology*; D005353:Fibronectins / Q000378:metabolism; D016257:Fura-2; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D008545:Melanoma; D008856:Microscopy, Fluorescence; D009361:Neoplasm Invasiveness; D010716:Phosphatidylinositols / Q000378:metabolism; D014407:Tumor Cells, Cultured
D002121:Calcium Channel Blockers; D005353:Fibronectins; D010716:Phosphatidylinositols; D003094:Collagen; D019204:GTP-Binding Proteins; D002118:Calcium; D016257:Fura-2