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Mitin N, Rossman KL, Currin R, Anne S, Marshall TW, Bear JE, Bautch VL, Der CJ. The RhoGEF TEM4 Regulates Endothelial Cell Migration by Suppressing Actomyosin Contractility. PLoS One 2013; 8:e66260. [PMID: 23825001 PMCID: PMC3688894 DOI: 10.1371/journal.pone.0066260] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 05/03/2013] [Indexed: 01/10/2023] Open
Abstract
Persistent cellular migration requires efficient protrusion of the front of the cell, the leading edge where the actin cytoskeleton and cell-substrate adhesions undergo constant rearrangement. Rho family GTPases are essential regulators of the actin cytoskeleton and cell adhesion dynamics. Here, we examined the role of the RhoGEF TEM4, an activator of Rho family GTPases, in regulating cellular migration of endothelial cells. We found that TEM4 promotes the persistence of cellular migration by regulating the architecture of actin stress fibers and cell-substrate adhesions in protruding membranes. Furthermore, we determined that TEM4 regulates cellular migration by signaling to RhoC as suppression of RhoC expression recapitulated the loss-of-TEM4 phenotypes, and RhoC activation was impaired in TEM4-depleted cells. Finally, we showed that TEM4 and RhoC antagonize myosin II-dependent cellular contractility and the suppression of myosin II activity rescued the persistence of cellular migration of TEM4-depleted cells. Our data implicate TEM4 as an essential regulator of the actin cytoskeleton that ensures proper membrane protrusion at the leading edge of migrating cells and efficient cellular migration via suppression of actomyosin contractility.
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Affiliation(s)
- Natalia Mitin
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- * E-mail:
| | - Kent L. Rossman
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Rachel Currin
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Sandeep Anne
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Thomas W. Marshall
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - James E. Bear
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Victoria L. Bautch
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- McAllister Heart Institute, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Channing J. Der
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina, United States of America
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Zeng G, Taylor SM, McColm JR, Kappas NC, Kearney JB, Williams LH, Hartnett ME, Bautch VL. Orientation of endothelial cell division is regulated by VEGF signaling during blood vessel formation. Blood 2006; 109:1345-52. [PMID: 17068148 PMCID: PMC1794069 DOI: 10.1182/blood-2006-07-037952] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
New blood vessel formation requires the coordination of endothelial cell division and the morphogenetic movements of vessel expansion, but it is not known how this integration occurs. Here, we show that endothelial cells regulate division orientation during the earliest stages of blood vessel formation, in response to morphogenetic cues. In embryonic stem (ES) cell-derived vessels that do not experience flow, the plane of endothelial cytokinesis was oriented perpendicular to the vessel long axis. We also demonstrated regulated cleavage orientation in vivo, in flow-exposed forming retinal vessels. Daughter nuclei moved away from the cleavage plane after division, suggesting that regulation of endothelial division orientation effectively extends vessel length in these developing vascular beds. A gain-of-function mutation in VEGF signaling increased randomization of endothelial division orientation, and this effect was rescued by a transgene, indicating that regulation of division orientation is a novel mechanism whereby VEGF signaling affects vessel morphogenesis. Thus, our findings show that endothelial cell division and morphogenesis are integrated in developing vessels by flow-independent mechanisms that involve VEGF signaling, and this cross talk is likely to be critical to proper vessel morphogenesis.
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Affiliation(s)
- Gefei Zeng
- Department of Biology, University of North Carolina at Chapel Hill 27599, USA
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Roberts DM, Anderson AL, Hidaka M, Swetenburg RL, Patterson C, Stanford WL, Bautch VL. A vascular gene trap screen defines RasGRP3 as an angiogenesis-regulated gene required for the endothelial response to phorbol esters. Mol Cell Biol 2004; 24:10515-28. [PMID: 15572660 PMCID: PMC533983 DOI: 10.1128/mcb.24.24.10515-10528.2004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We identified Ras guanine-releasing protein 3 (RasGRP3) as a guanine exchange factor expressed in blood vessels via an embryonic stem (ES) cell-based gene trap screen to identify novel vascular genes. RasGRP3 is expressed in embryonic blood vessels, down-regulated in mature adult vessels, and reexpressed in newly formed vessels during pregnancy and tumorigenesis. This expression pattern is consistent with an angiogenic function for RasGRP3. Although a loss-of-function mutation in RasGRP3 did not affect viability, RasGRP3 was up-regulated in response to vascular endothelial growth factor (VEGF) stimulation of human umbilical vein endothelial cells, placing RasGRP3 regulation downstream of VEGF signaling. Phorbol esters mimic the second messenger diacylglycerol (DAG) in activating both protein kinase C (PKC) and non-PKC phorbol ester receptors such as RasGRP3. ES cell-derived wild-type blood vessels exposed to phorbol myristate acetate (PMA) underwent extensive aberrant morphogenesis that resulted in the formation of large endothelial sheets rather than properly branched vessels. This response to PMA was completely dependent on the presence of RasGRP3, as mutant vessels were refractory to the treatment. Taken together, these findings show that endothelial RasGRP3 is up-regulated in response to VEGF stimulation and that RasGRP3 functions as an endothelial cell phorbol ester receptor in a pathway whose stimulation perturbs normal angiogenesis. This suggests that RasGRP3 activity may exacerbate vascular complications in diseases characterized by excess DAG, such as diabetes.
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Affiliation(s)
- David M Roberts
- Curriculum in Genetics and Molecular Biology, Department of Biology, CB#3280, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Roberts DM, Kearney JB, Johnson JH, Rosenberg MP, Kumar R, Bautch VL. The vascular endothelial growth factor (VEGF) receptor Flt-1 (VEGFR-1) modulates Flk-1 (VEGFR-2) signaling during blood vessel formation. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 164:1531-5. [PMID: 15111299 PMCID: PMC1615669 DOI: 10.1016/s0002-9440(10)63711-x] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mice lacking the vascular endothelial growth factor (VEGF) receptor flt-1 (VEGFR-1) die from vascular overgrowth, caused primarily by aberrant endothelial cell division (Kearney JB, Ambler CA, Monaco KA, Johnson N, Rapoport RG, Bautch VL: Vascular endothelial growth factor receptor Flt-1 negatively regulates developmental blood vessel formation by modulating endothelial cell division. Blood 2002, 99:2397-2407). Because a second high-affinity VEGF receptor, flk-1, produces a positive endothelial proliferation signal, it was logical to ask whether flt-1 affects developmental blood vessel formation by modulating signaling through flk-1. Differentiated embryonic stem cell cultures lacking flt-1 (flt-1-/-) had increased flk-1 tyrosine phosphorylation, indicating that flk-1 signaling is up-regulated in the mutant background. The selective flk-1 inhibitor SU5416 partially rescued the flt-1-/- mutant phenotype, and this rescue was accompanied by a decrease in the relative amount of flk-1 tyrosine phosphorylation. Thus reduced flk-1 signal transduction can partially compensate for the lack of flt-1. The flt-1-/- mutant phenotype was also partially rescued by Flt-1/Fc, a truncated flt-1 that binds and sequesters the VEGF ligand. Taken together, these data show that down-regulation of flk-1 signaling by two different strategies partially rescues the developmental vascular overgrowth seen in the absence of flt-1, and they support a model whereby flt-1 modulates the flk-1 signal at an early point in the pathway.
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Affiliation(s)
- David M Roberts
- Program in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill 27599, USA
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Moser M, Binder O, Wu Y, Aitsebaomo J, Ren R, Bode C, Bautch VL, Conlon FL, Patterson C. BMPER, a novel endothelial cell precursor-derived protein, antagonizes bone morphogenetic protein signaling and endothelial cell differentiation. Mol Cell Biol 2003; 23:5664-79. [PMID: 12897139 PMCID: PMC166349 DOI: 10.1128/mcb.23.16.5664-5679.2003] [Citation(s) in RCA: 184] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The development of endothelial cell precursors is essential for vasculogenesis. We screened for differentially expressed transcripts in endothelial cell precursors in developing mouse embryoid bodies. We cloned a complete cDNA encoding a protein that contains an amino-terminal signal peptide, five cysteine-rich domains, a von Willebrand D domain, and a trypsin inhibitor domain. We termed this protein BMPER (bone morphogenetic protein [BMP]-binding endothelial cell precursor-derived regulator). BMPER is specifically expressed in flk-1-positive cells and parallels the time course of flk-1 induction in these cells. In situ hybridization in mouse embryos demonstrates dorsal midline staining and staining of the aorto-gonadal-mesonephric region, which is known to host vascular precursor cells. BMPER is a secreted protein that directly interacts with BMP2, BMP4, and BMP6 and antagonizes BMP4-dependent Smad5 activation. In Xenopus embryos, ventral injection of BMPER mRNA results in axis duplication and downregulation of the expression of Xvent-1 (downstream target of Smad signaling). In an embryoid body differentiation assay, BMP4-dependent differentiation of endothelial cells in embryoid bodies is also antagonized by BMPER. Taken together, our data indicate that BMPER is a novel BMP-binding protein that is expressed by endothelial cell precursors, has BMP-antagonizing activity, and may play a role in endothelial cell differentiation by modulating local BMP activity.
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Affiliation(s)
- Martin Moser
- Carolina Cardiovascular Biology Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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Wu Y, Moser M, Bautch VL, Patterson C. HoxB5 is an upstream transcriptional switch for differentiation of the vascular endothelium from precursor cells. Mol Cell Biol 2003; 23:5680-91. [PMID: 12897140 PMCID: PMC166331 DOI: 10.1128/mcb.23.16.5680-5691.2003] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Endothelial cells differentiate from mesoderm-derived precursors to initiate the earliest events in vascular development. Although the signaling events that regulate the successive steps of vascular development are known in some detail, the transcriptional processes that regulate the first steps in vasculogenesis are not well defined. We have studied the regulatory mechanisms of flk1 expression as a model to understand the upstream events in endothelial cell differentiation, since flk1 is the earliest marker of endothelial precursors. Using a variety of biochemical approaches, we identified a cis-acting element in the first intron of the flk1 gene that is required for endothelium-dependent expression in transgenic reporter gene assays. Using the yeast one-hybrid system, we identified HoxB5 as the transcription factor that binds this cis-acting element, the HoxB5-binding element (HBE). HoxB5 mRNA colocalized with flk1 expression in differentiating embryoid bodies, and HoxB5 potently transactivated the flk1 promoter in an HBE-dependent fashion in transient-transfection assays. Overexpression of HoxB5 led to expansion of flk1(+) angioblasts in differentiating embryoid bodies and increased the number of PECAM (platelet-endothelial cell adhesion molecule)-positive primitive blood vessels. HoxB5 is necessary and sufficient to activate the cell-intrinsic events that regulate the differentiation of angioblasts and mature endothelial cells from their mesoderm-derived precursors.
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Affiliation(s)
- Yaxu Wu
- Carolina Cardiovascular Biology Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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Ambler CA, Schmunk GM, Bautch VL. Stem cell-derived endothelial cells/progenitors migrate and pattern in the embryo using the VEGF signaling pathway. Dev Biol 2003; 257:205-19. [PMID: 12710968 DOI: 10.1016/s0012-1606(03)00042-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Endothelial precursor cells respond to molecular cues to migrate and assemble into embryonic blood vessels, but the signaling pathways involved in vascular patterning are not well understood. We recently showed that avian vascular patterning cues are recognized by mammalian angioblasts derived from somitic mesoderm through analysis of mouse-avian chimeras. To determine whether stem cell-derived endothelial cells/progenitors also recognize global patterning signals, murine ES cell-derived embryoid bodies (EBs) were grafted into avian hosts. ES cell-derived murine endothelial cells/progenitors migrated extensively and colonized the appropriate host vascular beds. They also formed mosaic vessels with avian endothelial cells. Unlike somite derived-endothelial cells, ES cell-derived endothelial cells/progenitors migrated across the host embryonic midline to the contralateral side. To determine the role of VEGF signaling in embryonic vascular patterning, EBs mutant for a VEGF receptor (flk-1(-/-)) or a signal (VEGF-A(-/-)) were grafted into quail hosts. Flk-1(-/-) EB grafts produced only rare endothelial cells that did not migrate or assemble into vessels. In contrast, VEGF-A(-/-) EB grafts produced endothelial cells that resembled wild-type and colonized host vascular beds, suggesting that host-derived signals can partially rescue mutant graft vascular patterning. VEGF-A(-/-) graft endothelial cells/progenitors crossed the host midline with much lower frequency than wild-type EB grafts, indicating that graft-derived VEGF compromised the midline barrier when present. Thus, ES cell-derived endothelial cells/progenitors respond appropriately to global vascular patterning cues, and they require the VEGF signaling pathway to pattern properly. Moreover, EB-avian chimeras provide an efficient way to screen mutations for vascular patterning defects.
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Affiliation(s)
- Carrie A Ambler
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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