title: Virion stiffness regulates immature HIV-1 entry.
abstract: BACKGROUND
  Human immunodeficiency virus type 1 (HIV-1) undergoes a protease-mediated maturation process that is required for its infectivity. Little is known about how the physical properties of viral particles change during maturation and how these changes affect the viral lifecycle. Using Atomic Force Microscopy (AFM), we previously discovered that HIV undergoes a "stiffness switch", a dramatic reduction in particle stiffness during maturation that is mediated by the viral Envelope (Env) protein.
  
  
  RESULTS
  In this study, we show that transmembrane-anchored Env cytoplasmic tail (CT) domain is sufficient to regulate the particle stiffness of immature HIV-1. Using this construct expressed in trans with viral Env lacking the CT domain, we show that increasing particle stiffness reduces viral entry activity in immature virions. A similar effect was also observed for immature HIV-1 pseudovirions containing Env from vesicular stomatitis virus.
  
  
  CONCLUSIONS
  This linkage between particle stiffness and viral entry activity illustrates a novel level of regulation for viral replication, providing the first evidence for a biological role of virion physical properties and suggesting a new inhibitory strategy.
authors.affiliation: Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112-5650, USA.
authors.forename: Hong-Bo
authors.initials: HB
authors.lastname: Pang
authors.forename: Liron
authors.initials: L
authors.lastname: Hevroni
authors.forename: Nitzan
authors.initials: N
authors.lastname: Kol
authors.forename: Debra M
authors.initials: DM
authors.lastname: Eckert
authors.forename: Marianna
authors.initials: M
authors.lastname: Tsvitov
authors.forename: Michael S
authors.initials: MS
authors.lastname: Kay
authors.forename: Itay
authors.initials: I
authors.lastname: Rousso
mesh_terms: D015497:HIV-1 / Q000472:pathogenicity*; D006801:Humans; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D014763:Viral Matrix Proteins / Q000502:physiology; D014771:Virion / Q000737:chemistry / Q000472:pathogenicity*; D053586:Virus Internalization; D014779:Virus Replication / Q000502:physiology; D054299:env Gene Products, Human Immunodeficiency Virus / Q000737:chemistry; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000737:chemistry / Q000502:physiology
chemical_list: D014763:Viral Matrix Proteins; D054299:env Gene Products, Human Immunodeficiency Virus; D054301:gag Gene Products, Human Immunodeficiency Virus