Site-1 protease-mediated lipid metabolism in lymphatic vascular development
Biography
Overview
The?lymphatic?vascular?system?is?essential?for?transporting?interstitial?fluid,?dietary?fat,?and?immune?cells.?Defects? in?these?functions?contribute?to?lymphedema,?impaired?lipid?absorption,?obesity,?abnormal?immune?function,?and? cancer?metastasis.?During?embryonic?development,?lymphangiogenesis?is?robust,?primarily?driven?by?vascular? endothelial?growth?factor?C?(VEGF-?C)-?mediated?activation?of?VEGFR-?3,?a?main?VEGF-?C?receptor?on?lymphatic? endothelial?cells?(LECs).?Emerging?evidence?has?shown?the?metabolism?of?endothelial?cells?is?critical?for?vascular? development.?Changes?in?EC?metabolic?pathways?are?found?in?pathologies?such?as?cancer?and?diabetes?as?well.?But? most?research?has?been?focused?on?blood?endothelial?metabolic?pathways.?Despite?a?few?recent?pioneering?studies,? knowledge?of?LEC?metabolism?during?lymphangiogenesis?is?limited.?There?is?an?unmet?need?to?bridge?the?knowledge? gap?between?cellular?metabolism?and?lymphatic?vascular?development.?Site-?1?protease?(S1P),?encoded?by? membrane-?bound?transcription?factor?peptidase,?site?1?(MBTPS1),?is?a?serine?protease?in?the?Golgi?apparatus.?S1P?is? a?key?regulator?of?cholesterol?biosynthesis?by?proteolytic?activation?of?a?membrane-?bound?latent?transcription?factor,? sterol-?regulatory?element?binding?protein?2?(SREBP2).?Recently,?we?found?that?mice?with?inducible?endothelial?cell-? specific?deficiency?of?S1P?(iEC?Mbtps1-?/-?,?Mbtps1f/f;?Cdh5CreERT2)?exhibited?severe?subcutaneous?lymphedema?and? defective?lymphatic?vasculature?during?development.?Our?pilot?experiments?also?showed?that?mice?with?LEC-?specific? deficiency?of?SREBP2?(LEC?Srebf2-?/-?,?Srebf2f/f;?Lyve1Cre)?had?a?similar?lymphatic?vascular?defect?during? development.?These?strong?in?vivo?preliminary?data?support?the?central?hypothesis?that?S1P/SREBP2-?mediated? cholesterol?biosynthesis?is?required?for?lymphatic?vascular?development.? We?will?test?the?central?hypothesis?through?two?Aims:?1)?determine?whether?lymphatic?endothelial?S1P/SREBP2-? mediated?cholesterol?biosynthesis?is?required?for?lymphatic?vascular?development.?We?will?characterize?LEC?cellular? defects,?such?as?differentiation,?migration,?and?proliferation,?of?S1P?or?SREBP2-?deficient?mice?at?different?stages?of? embryonic?development.?These?in?vivo?analyses?will?be?complemented?by?in?vitro?assays?using?LECs?isolated?from? wild-?type?(WT)?or?mutant?mice?as?well?as?primary?human?LECs;??2)?determine?mechanisms?by?which?S1P/SREBP2-? mediated?cholesterol?biosynthesis?regulate?lymphangiogenesis.?Based?on?our?preliminary?results,?we?will?primarily? test?the?hypothesis?S1P/SREBP2-?mediated?cholesterol?biosynthesis?is?required?for?sustained?VEGFR3?signaling? mainly?by?in?vitro?assays?using?WT?or?mutant?LECs?as?well?as?human?LECs?with?knockdown?of?S1P/SREBP2?or? functional?inhibitors?to?S1P?and?SREBP2.? Based?on?strong?preliminary?data,?our?proposed?study?will?reveal?novel?insights?into?roles?of?S1P-?mediated?lipid? metabolism?in?lymphatic?vascular?development.?Our?study?may?lead?to?novel?therapeutic?opportunities?for? pathologies?with?lymphatic?vascular?defects.?? ?
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