title: TRPC6 is the endothelial calcium channel that regulates leukocyte transendothelial migration during the inflammatory response.
abstract: Leukocyte transendothelial migration (TEM) is a tightly regulated, multistep process that is critical to the inflammatory response. A transient increase in endothelial cytosolic free calcium ion concentration (↑[Ca(2+)]i) is required for TEM. However, the mechanism by which endothelial ↑[Ca(2+)]i regulates TEM and the channels mediating this ↑[Ca(2+)]i are unknown. Buffering ↑[Ca(2+)]i in endothelial cells does not affect leukocyte adhesion or locomotion but selectively blocks TEM, suggesting a role for ↑[Ca(2+)]i specifically for this step. Transient receptor potential canonical 6 (TRPC6), a Ca(2+) channel expressed in endothelial cells, colocalizes with platelet/endothelial cell adhesion molecule-1 (PECAM) to surround leukocytes during TEM and clusters when endothelial PECAM is engaged. Expression of dominant-negative TRPC6 or shRNA knockdown in endothelial cells arrests neutrophils apically over the junction, similar to when PECAM is blocked. Selectively activating endothelial TRPC6 rescues TEM during an ongoing PECAM blockade, indicating that TRPC6 functions downstream of PECAM. Furthermore, endothelial TRPC6 is required for trafficking of lateral border recycling compartment membrane, which facilitates TEM. Finally, mice lacking TRPC6 in the nonmyeloid compartment (i.e., endothelium) exhibit a profound defect in neutrophil TEM with no effect on leukocyte trafficking. Our findings identify endothelial TRPC6 as the calcium channel mediating the ↑[Ca(2+)]i required for TEM at a step downstream of PECAM homophilic interactions.
authors.affiliation: Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611.
authors.forename: Evan W
authors.initials: EW
authors.lastname: Weber
authors.affiliation: Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611.
authors.forename: Fei
authors.initials: F
authors.lastname: Han
authors.affiliation: Department of Pharmacology, Center for Lung and Vascular Biology, University of Illinois in Chicago College of Medicine, Chicago, IL 60612.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Tauseef
authors.affiliation: Neurobiology Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
authors.forename: Lutz
authors.initials: L
authors.lastname: Birnbaumer
authors.affiliation: Department of Pharmacology, Center for Lung and Vascular Biology, University of Illinois in Chicago College of Medicine, Chicago, IL 60612.
authors.forename: Dolly
authors.initials: D
authors.lastname: Mehta
authors.affiliation: Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611 wamuller@northwestern.edu.
authors.forename: William A
authors.initials: WA
authors.lastname: Muller
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002465:Cell Movement; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D042783:Endothelial Cells / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D007962:Leukocytes / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000502:physiology; D050052:TRPC Cation Channels / Q000502:physiology*; D000074287:TRPC6 Cation Channel
chemical_list: D019408:Platelet Endothelial Cell Adhesion Molecule-1; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C492146:Trpc6 protein, mouse; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D002118:Calcium