The Study On The Regulatory Mechanism Of Lipid Rafts In Human Melanoma Cell Migration

Metastasis is the major cause of cancer mortality. To successfully metastasize, cancercells must use their intrinsic migratory ability to invade adjacent tissues and the vasculature.Therefore, the migration of cancer cells is the prerequisite for metastasis and understandingthe molecular mechanisms regulating the migration of cancer cells is very important foranti-metastasis therapy.The migration of cancer cells on substrate is the sum of several temporally and spatiallycoordinated processes, which include protrusion of the leading edge, adhesion of the leadingedge to the substrate, movement of cell body, and release from contact sites at the trailingedge. During these processes, the dynamics of actin cytoskeleton and focal adhesion aregenerally thought to play pivotal roles. The remodeling of actin cytoskeleton provides adriving force to push membrane forward at the leading edge and a traction force to move thecell body. The formation of focal adhesions at cell front anchors membrane protrusions andtheir disassembly at the rear of the cells is required for cell relocation and forwardprogression. Furthermore, actin cytoskeleton shows a close relationship with focal adhesionin cell migration. Actin cytoskeleton regulates the formation and stability of focal adhesion.Thus, the factors influencing the remodeling of actin cytoskeleton are also potentialregulators of focal adhesion dynamics. Lipid rafts, cholesterol and sphingolipid enrichedmembrane microdomains, form compartmental platforms for cellular signaling andprotein-protein or protein-lipid interaction. Previous reports showed that lipid rafts canconcentrate membrane lipids and some proteins, and regulate the dynamics of actincytoskeleton in T cell activation and neurites growth. However, whether lipid rafts regulatefocal adhesion dynamics through modulating actin cytoskeleton in cancer cell migration andthe underlying mechanisms have not been well characterized.In the present study, using wound healing assay, we found that the disruption of lipidrafts inhibit the migration and morphological change in human melanoma A375and M21cells. The results of immunofluescence and live cell imaging analysis showed that disruptingthe integrity of lipid rafts enhances actin stress fiber formation and inhibits focal adhesion disassembly. The further investigation indicated that actin cytoskeleton mediates the lipidraft-dependent focal adhesion disassembly by regulating the dephosphorylation of focaladhesion proteins paxillin and vinculin and the internalization of β3integrin-the structuralcore of focal adhesion. We also showed that Src-RhoA-Rho kinase signaling pathway isresponsible for lipid raft-dependent actin cytoskeleton dynamics. Taken together, wedemonstrated that lipid rafts regulate melanoma cell migration through actincytoskeleton-regulated focal adhesion disassembly.