title: Nanopodia--thin, fragile membrane projections with roles in cell movement and intercellular interactions.
abstract: Adherent cells in culture maintain a polarized state to support movement and intercellular interactions. Nanopodia are thin, elongated, largely F-actin-negative membrane projections in endothelial and cancer cells that can be visualized through TM4SF1 (Transmembrane-4-L-six-family-1) immunofluorescence staining. TM4SF1 clusters in 100-300 μm diameter TMED (TM4SF1 enriched microdomains) containing 3 to as many as 14 individual TM4SF1 molecules. TMED are arranged intermittently along nanopodia at a regular spacing of 1 to 3 TMED per μm and firmly anchor nanopodia to matrix. This enables nanopodia to extend more than 100 μm from the leading front or trailing rear of polarized endothelial or tumor cells, and causes membrane residues to be left behind on matrix when the cell moves away. TMED and nanopodia have been overlooked because of their extreme fragility and sensitivity to temperature. Routine washing and fixation disrupt the structure. Nanopodia are preserved by direct fixation in paraformaldehyde (PFA) at 37 °C, followed by brief exposure to 0.01% Triton X-100 before staining. Nanopodia open new vistas in cell biology: they promise to reshape our understanding of how cells sense their environment, detect and identify other cells at a distance, initiate intercellular interactions at close contact, and of the signaling mechanisms involved in movement, proliferation, and cell-cell communications. The methods that are developed for studying TM4SF1-derived nanopodia may be useful for studies of nanopodia that form in other cell types through the agency of classic tetraspanins, notably the ubiquitously expressed CD9, CD81, and CD151.
authors.affiliation: Center for Vascular Biology Research, Department of of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School.
authors.forename: Chi-Iou
authors.initials: CI
authors.lastname: Lin
authors.affiliation: Center for Vascular Biology Research, Department of of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School.
authors.forename: Chun-Yee
authors.initials: CY
authors.lastname: Lau
authors.affiliation: Center for Vascular Biology Research, Department of of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: Center for Vascular Biology Research, Department of of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School; sjaminet@bidmc.harvard.edu.
authors.forename: Shou-Ching
authors.initials: SC
authors.lastname: Jaminet
mesh_terms: D000954:Antigens, Surface / Q000032:analysis; D002450:Cell Communication / Q000502:physiology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D003584:Cytological Techniques / Q000379:methods*; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D009363:Neoplasm Proteins / Q000032:analysis; D017830:Octoxynol / Q000737:chemistry; D011554:Pseudopodia / Q000502:physiology*
chemical_list: D000954:Antigens, Surface; D009363:Neoplasm Proteins; C074075:TM4SF1 protein, human; D017830:Octoxynol
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