title: KSHV gB associated RGD interactions promote attachment of cells by inhibiting the potential migratory signals induced by the disintegrin-like domain.
abstract: BACKGROUND
  Kaposi's sarcoma-associated herpesvirus (KSHV) glycoprotein B (gB) is not only expressed on the envelope of mature virions but also on the surfaces of cells undergoing lytic replication. Among herpesviruses, KSHV gB is the only glycoprotein known to possess the RGD (Arg-Gly-Asp) binding integrin domain critical to mediating cell attachment. Recent studies described gB to also possess a disintegrin-like domain (DLD) said to interact with non-RGD binding integrins. We wanted to decipher the roles of two individually distinct integrin binding domains (RGD versus DLD) within KSHV gB in regulating attachment of cells over cell migration.
  
  
  METHODS
  We established HeLa cells expressing recombinant full length gB, gB lacking a functional RGD (gBΔR), and gB lacking a functionally intact DLD (gBΔD) on their cell surfaces. These cells were tested in wound healing assay, Transwell migration assay, and adhesion assay to monitor the ability of the RGD and DLD integrin recognition motifs in gB to mediate migration and attachment of cells. We also used soluble forms of the respective gB recombinant proteins to analyze and confirm their effect on migration and attachment of cells. The results from the above studies were authenticated by the use of imaging, and standard biochemical approaches as Western blotting and RNA silencing using small interfering RNA.
  
  
  RESULTS
  The present report provides the following novel findings: (i) gB does not induce cell migration; (ii) RGD domain in KSHV gB is the switch that inhibits the ability of DLD to induce cellular migration thus promoting attachment of cells.
  
  
  CONCLUSIONS
  Independently, RGD interactions mediate attachment of cells while DLD interactions regulate migration of cells. However, when both RGD and DLD are functionally present in the same protein, gB, the RGD interaction-induced attachment of cells overshadows the ability of DLD mediated signaling to induce migration of cells. Furthering our understanding of the molecular mechanism of integrin engagement with RGD and DLD motifs within gB could identify promising new therapeutic avenues and research areas to explore.
authors.affiliation: Department of Microbiology & Immunology, Brody School of Medicine at East Carolina University, Greenville, NC, 27834, USA.
authors.forename: Hosni A M
authors.initials: HAM
authors.lastname: Hussein
authors.affiliation: Department of Microbiology & Immunology, Brody School of Medicine at East Carolina University, Greenville, NC, 27834, USA.
authors.forename: Lia R
authors.initials: LR
authors.lastname: Walker
authors.affiliation: Department of Microbiology & Immunology, Brody School of Medicine at East Carolina University, Greenville, NC, 27834, USA. akulas@ecu.edu.
authors.forename: Shaw M
authors.initials: SM
authors.lastname: Akula
mesh_terms: D001665:Binding Sites; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D006023:Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D019288:Herpesvirus 8, Human / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D006023:Glycoproteins; D014759:Viral Envelope Proteins