title: Thioredoxin-interacting protein is a biomechanical regulator of Src activity: key role in endothelial cell stress fiber formation.
abstract: BACKGROUND
  Fluid shear stress differentially regulates endothelial cell stress fiber formation with decreased stress fibers in areas of disturbed flow compared with steady flow areas. Importantly, stress fibers are critical for several endothelial cell functions including cell shape, mechano-signal transduction, and endothelial cell-cell junction integrity. A key mediator of steady flow-induced stress fiber formation is Src that regulates downstream signaling mediators such as phosphorylation of cortactin, activity of focal adhesion kinase, and small GTPases.
  
  
  OBJECTIVE
  Previously, we showed that thioredoxin-interacting protein (TXNIP, also VDUP1 [vitamin D upregulated protein 1] and TBP-2 [thioredoxin binding protein 2]) was regulated by fluid shear stress; TXNIP expression was increased in disturbed flow compared with steady flow areas. Although TXNIP was originally characterized for its role in redox and metabolic cellular functions, recent reports show important scaffold functions related to its α-arrestin structure. Based on these findings, we hypothesized that TXNIP acts as a biomechanical sensor that regulates Src kinase activity and stress fiber formation.
  
  
  RESULTS
  Using en face immunohistochemistry of the aorta and cultured endothelial cells, we show inverse relationship between TXNIP expression and Src activity. Specifically, steady flow increased Src activity and stress fiber formation, whereas it decreased TXNIP expression. In contrast, disturbed flow had opposite effects. We studied the role of TXNIP in regulating Src homology phosphatase-2 plasma membrane localization and vascular endothelial cadherin binding because Src homology phosphatase-2 indirectly regulates dephosphorylation of Src tyrosine 527 that inhibits Src activity. Using immunohistochemistry and immunoprecipitation, we found that TXNIP prevented Src homology phosphatase-2-vascular endothelial cadherin interaction.
  
  
  CONCLUSIONS
  In summary, these data characterize a fluid shear stress-mediated mechanism for stress fiber formation that involves a TXNIP-dependent vascular endothelial cadherin-Src homology phosphatase-2-Src pathway.
authors: From the Departments of Medicine (O.N.S., R.M.B., C.Y., B.C.B.) and Pharmacology and Physiology (O.N.S., C.Y., B.C.B.), University of Rochester School of Medicine and Dentistry, Aab Cardiovascular Research Institute, NY.
authors: Oded N
authors: ON
authors: Spindel
authors: Ryan M
authors: RM
authors: Burke
authors: Chen
authors: C
authors: Yan
authors: Bradford C
authors: BC
authors: Berk
mesh_terms: D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism*; D006801:Humans; D051379:Mice; D011485:Protein Binding; D021381:Protein Transport; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases / Q000378:metabolism; D022502:Stress Fibers / Q000378:metabolism*; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D015820:Cadherins; D002352:Carrier Proteins; C445672:Txnip protein, mouse; D013879:Thioredoxins; D019061:src-Family Kinases; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases
keywords: TXNIP; disturbed flow; endothelial cells; laminar flow; stress fibers