title: Secretion of soluble vascular endothelial growth factor receptor 1 (sVEGFR1/sFlt1) requires Arf1, Arf6, and Rab11 GTPases.
abstract: The soluble form of vascular endothelial growth factor receptor 1 (sVEGFR-1/sFlt1) is generated by alternative splicing of the FLT1 gene. Secretion of sFlt1 from endothelial cells plays an important role in blood vessel sprouting and morphogenesis. However, excess sFlt1 secretion is associated with diseases such as preeclampsia and chronic kidney disease. To date, the secretory transport process involved in the secretion of sFlt1 is poorly understood. In the present study, we investigated the itinerary of sFlt1 trafficking along the secretory pathway. To understand the timecourse of sFlt1 secretion, endothelial cells stably expressing sFlt1 were metabolically radiolabeled with [(35)S]-methionine and cysteine. Our results indicate that after initial synthesis the levels of secreted [(35)S]-sFlt1 in the extracellular medium peaks at 8 hours. Treatment with brefeldin A (BFA), a drug which blocks trafficking between the endoplasmic reticulum (ER) and the Golgi complex, inhibited extracellular release of sFlt1 suggesting that ER to Golgi and intra-Golgi trafficking of sFlt1 are essential for its secretion. Furthermore, we show that ectopic expression of dominant-negative mutant forms of Arf1, Arf6, and Rab11 as well as siRNA-mediated knockdown of these GTPases block secretion of sFlt1 during normoxic and hypoxic conditions suggesting role for these small GTPases. This work is the first to report role of regulatory proteins involved in sFlt1 trafficking along the secretory pathway and may provide insights and new molecular targets for the modulation of sFlt-1 release during physiological and pathological conditions.
authors.affiliation: Departments of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Jae-Joon
authors.initials: JJ
authors.lastname: Jung
authors.forename: Ajit
authors.initials: A
authors.lastname: Tiwari
authors.forename: Shivangi M
authors.initials: SM
authors.lastname: Inamdar
authors.forename: Christie P
authors.initials: CP
authors.lastname: Thomas
authors.forename: Apollina
authors.initials: A
authors.lastname: Goel
authors.forename: Amit
authors.initials: A
authors.lastname: Choudhury
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D020126:Brefeldin A / Q000494:pharmacology; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006056:Golgi Apparatus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D010957:Plasmids; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D012995:Solubility; D013462:Sulfur Radioisotopes; D014162:Transfection; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000235:genetics* / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D020823:ADP-Ribosylation Factor 1; D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors; D000596:Amino Acids; D020126:Brefeldin A; D011500:Protein Synthesis Inhibitors; D034741:RNA, Small Interfering; D013462:Sulfur Radioisotopes; D040281:Vascular Endothelial Growth Factor Receptor-1; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C000715348:ARF6 protein, human