Vascular endothelial cells (VEC) assemble into capillary-like structures during angiogenesis, and this neovascularization process plays an important role in a wide range of physiological and pathological scenarios. Based on significant upregulation of its expression in VEC during capillary morphogenesis, profilin-1 (Pfn1 - a ubiquitously expressed actin-binding protein) was previously implicated in capillary morphogenesis of VEC. The overall objective of the present study was to investigate whether and how loss of Pfn1 function affects a) the various cellular functions that are important for capillary morphogenesis such as VEC migration, invasion and proliferation, and b) the overall capillary forming ability of VEC. Loss of Pfn1 function in VEC was achieved either by suppressing the overall expression of Pfn1 by RNA interference method or selectively abrogating specific ligand-interactions (actin, proline-rich ligands) of Pfn1 by expressing various point-mutants of Pfn1 in a near-null endogenous Pfn1 background (knockdown and knock-in approach). Loss of Pfn1 expression causes a major change in actin cytoskeleton in VEC. Particularly, there is a significant depletion of actin filaments and focal adhesions in VEC when Pfn1 expression was silenced. Silencing of Pfn1 expression also significantly impairs the migratory ability of VEC. Analyses of leading edge dynamics revealed that Pfn1 depletion results in decreased velocity and frequency of lamellipodial protrusion. Further experiments with point-mutants of Pfn1 showed that both actin and polyproline interactions of Pfn1 are required for efficient lamellipodial protrusion and overall migration of VEC. Loss of Pfn1 expression is associated with reduced dynamics of VE-cadherin dependent cell-cell adhesion, which was also found to be correlated with increased nuclear accumulation of p27 Kip1 (a major cell-cycle inhibitor) and reduced VEC proliferation. Finally, we found that loss of overall expression of Pfn1 significantly impairs collagen gel invasion and three-dimensional (3-D) capillary morphogenesis of VEC. Abolishing either of actin or polyproline interactions of Pfn1 also leads to a dramatic inhibition of capillary mophogenesis of VEC. Taken together, these results demonstrate that Pfn1 plays a critical role in capillary morphogenesis of VEC through its interactions with both actin and polyproline ligands. This study may further imply that Pfn1 could be a novel angiogenesis target.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-03262009-155327 |
| Date | 29 June 2009 |
| Creators | Ding, Zhijie |
| Contributors | Song Li, Partha Roy, Tao Cheng, Lance Davidson, Johnny Huard |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-03262009-155327/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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