Loss of Caveolin-1 Polarity Impedes Endothelial Cell Polarization and Directional Movement

Abstract

The ability of a cell to move requires the asymmetrical organization of cellular activities. To investigate polarized cellular activity in moving endothelial cells, human endothelial cells were incubated in a Dunn chamber to allow migration toward vascular endothelial growth factor. Immunofluorescent staining with a specific antibody against caveolin-1 revealed that caveolin-1 was concentrated at the rear of moving cells. Similarly, monolayer scraping to induce random cell walk resulted in relocation of caveolin-1 to the cell rear. These results suggest that posterior polarization of caveolin-1 is a common feature both for chemotaxis and chemokinesis. Dual immunofluorescent labeling showed that, during cell spreading, caveolin-1 was compacted in the cell center and excluded from nascent focal contacts along the circular lamellipodium, as revealed by integrin ␤ 1 and FAK staining. When cells were migrating, integrin ␤ 1 and FAK appeared at polarized lamellipodia, whereas caveolin-1 was found at the posterior of moving cells. Notably, wherever caveolin-1 was polarized, there was a conspicuous absence of lamellipod protrusion. Transmission electron microscopy showed that caveolae, similar to their marker caveolin-1, were located at the cell center during cell spreading or at the cell rear during cell migration. In contrast to its unphosphorylated form, tyrosine-phosphorylated caveolin-1, upon fibronectin stimulation, was associated with the focal complex molecule phosphopaxillin along the lamellipodia of moving cells. Thus, unphosphorylated and phosphorylated caveolin-1 were located at opposite poles during cell migration. Importantly, loss of caveolin-1 polarity by targeted down-regulation of the protein prevented cell polarization and directional movement. Our present results suggest a potential role of caveolin polarity in lamellipod extension and cell migration.

On the move: endocytic trafficking in cell migration

“…In the case of caveolin-mediated endocytosis the main component, Cav1, has been shown to localize predominantly to the cell rear during 2D migration [51,52]. This was confirmed by ultrastructural analyses finding the typical flask-like invaginated caveolae structures mainly localized at the trailing end [50].…”

Identification of a Novel Domain at the N Terminus of Caveolin-1 That Controls Rear Polarization of the Protein and Caveolae Formation

“…Human umbilical vein endothelial cells (HUVECs) were isolated from the human umbilical vein and cultured as described previously (24,26). The cells were grown in MCDB131 supplemented with 5% heat-inactivated human serum, 20% heat-inactivated newborn calf serum, 150 g/ml endothelial cell growth supplement, 5 units/ml heparin sodium, 100 units/ml penicillin, and 100 g/ml streptomycin.…”

“…We and others have shown recently that caveolae and Cav-1 are polarized in migrating endothelial cells (11,24,25). However, the mechanism underlying the asymmetrical distribution is not known.…”

“…It is proposed that polarized caveolae and Cav-1 may play an important role in spatial organization of polarized signaling activity during cell migration, given the fact that caveolae are rich in signaling molecules and actively travel in cells upon stimulation. Indeed, depolarization of Cav-1 by targeted knockdown of the protein significantly impedes cell polarization and inhibits cell directional movement (24). In an attempt to identify specific sequence(s) or domain(s) that controls Cav-1 rear polarization in migrating cells, we generated mutant forms of Cav-1 fused to the reporter protein GFP and expressed them in cells lacking endogenous Cav-1.…”

New Insights into 4-Amino-2-tri-fluoromethyl-phenyl Ester Inhibition of Cell Growth and Migration in the A549 Lung Adenocarcinoma Cell Line

“…It is still controversial about the role of CAV1 in tumor progression, especially for cell migration. In non-metastatic cells, for instance, fibroblasts, neurons and endothelial cells, CAV1 accumulates at the rear of the migrating cells (Beardsley et al, 2005;Sun et al, 2007;Lentini et al, 2008), while in metastatic cells, such as MDA-MB-231 human breast cancer cells and B16-F10 mouse melanoma, CAV1 does not accumulate at the edge during migration (Urra et al, 2012).…”