Lipid Raft Association Restricts CD44-Ezrin Interaction and Promotion of Breast Cancer Cell Migration

• Published in: The American journal of pathology Vol. 181; no. 6; pp. 2172 - 2187
• Main Authors: Donatello, Simona, Babina, Irina S, Hazelwood, Lee D, Hill, Arnold D.K, Nabi, Ivan R, Hopkins, Ann M
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.12.2012; American Society for Investigative Pathology
• Subjects: beta-Cyclodextrins - pharmacology; Biological and medical sciences; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Caveolin 1 - metabolism; Cell Compartmentation - drug effects; Cell Line, Tumor; Cell Movement - drug effects; Cytoskeletal Proteins - metabolism; Female; Gene Knockdown Techniques; Gynecology. Andrology. Obstetrics; Humans; Hyaluronan Receptors - metabolism; Hyaluronic Acid - pharmacology; Investigative techniques, diagnostic techniques (general aspects); Mammary gland diseases; Medical sciences; Membrane Microdomains - metabolism; Membrane Proteins - metabolism; Models, Biological; Pathology; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Protein Binding - drug effects; Protein Transport - drug effects; Regular; Subcellular Fractions - metabolism; Tumors; Transmembrane protein; Lipid raft; Breast disease; Interaction; Cell adhesion molecule; Ezrin; Breast cancer; Malignant tumor; Mammary gland diseases; Cell motility; Anatomic pathology; Association; Tumor cell; Cell migration; Cancer
• ISSN: 0002-9440; 1525-2191
• DOI: 10.1016/j.ajpath.2012.08.025

Cancer cell migration is an early event in metastasis, the main cause of breast cancer-related deaths. Cholesterol-enriched membrane domains called lipid rafts influence the function of many molecules, including the raft-associated protein CD44. We describe a novel mechanism whereby rafts regulate interactions between CD44 and its binding partner ezrin in migrating breast cancer cells. Specifically, in nonmigrating cells, CD44 and ezrin localized to different membranous compartments: CD44 predominantly in rafts, and ezrin in nonraft compartments. After the induction of migration (either nonspecific or CD44-driven), CD44 affiliation with lipid rafts was decreased. This was accompanied by increased coprecipitation of CD44 and active (threonine-phosphorylated) ezrin-radixin-moesin (ERM) proteins in nonraft compartments and increased colocalization of CD44 with the nonraft protein, transferrin receptor. Pharmacological raft disruption using methyl-β-cyclodextrin also increased CD44-ezrin coprecipitation and colocalization, further suggesting that CD44 interacts with ezrin outside rafts during migration. Conversely, promoting CD44 retention inside lipid rafts by pharmacological inhibition of depalmitoylation virtually abolished CD44-ezrin interactions. However, transient single or double knockdown of flotillin-1 or caveolin-1 was not sufficient to increase cell migration over a short time course, suggesting complex crosstalk mechanisms. We propose a new model for CD44-dependent breast cancer cell migration, where CD44 must relocalize outside lipid rafts to drive cell migration. This could have implications for rafts as pharmacological targets to down-regulate cancer cell migration.