title: Reconstitution and molecular analysis of an active human immunodeficiency virus type 1 Nef/p21-activated kinase 2 complex.
abstract: Human immunodeficiency virus type 1 (HIV-1) Nef activation of p21-activated kinase 2 (PAK-2) was recapitulated in a cell-free system consisting of in vitro-transcribed RNA, rabbit reticulocyte lysate, and microsomal membranes on the basis of the following observations: (i) Nef associated with a kinase endogenous to the rabbit reticulocyte lysate that was identified as PAK-2, (ii) Nef-associated kinase activity was detected with Nefs from HIV-1(SF2), HIV-1(YU2), and SIV(mac239), (iii) kinase activation was not detected with a myristoylation-defective Nef (HIV-1(SF2)NefG2A) or with a Nef defective in PAK-2 activation but fully competent in other Nef functions (HIV-1(SF2)NefF195I), and (iv) Nef-associated kinase activation required activated endogenous p21 GTPases (Rac1 or Cdc42). The cell-free system was used to analyze the mechanism of Nef activation of PAK-2. First, studies suggest that the p21 GTPases may act transiently to enhance Nef activation of PAK-2 in vitro. Second, addition of wortmannin to the cell-free system demonstrated that Nef activation of PAK-2 does not require PI 3-kinase activity. Third, ultracentrifugation analysis revealed that whereas the majority of Nef and PAK-2 partitioned to the supernatant, Nef-associated PAK-2 activity partitioned to the membrane-containing pellet as a low-abundance complex. Lastly, Nef activation of PAK-2 in vitro requires addition of microsomal membranes either during or after translation of the Nef RNA. These results are consistent with a model in which activation of PAK-2 by Nef occurs by recruiting PAK-2 to membranes. As demonstrated herein, the cell-free system is a new and important tool in the investigation of the mechanism of PAK-2 activation by Nef.
authors.affiliation: Department of Internal Medicine, Division of Infectious Diseases, University of Texas Southwestern Medical Center at Dallas, 75390-9113, USA.
authors.forename: Alexa
authors.initials: A
authors.lastname: Raney
authors.forename: Lillian S
authors.initials: LS
authors.lastname: Kuo
authors.forename: Laura L
authors.initials: LL
authors.lastname: Baugh
authors.forename: John L
authors.initials: JL
authors.lastname: Foster
authors.forename: J Victor
authors.initials: JV
authors.lastname: Garcia
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D002474:Cell-Free System; D004789:Enzyme Activation; D015693:Gene Products, nef / Q000378:metabolism*; D015658:HIV Infections / Q000821:virology*; D015497:HIV-1 / Q000201:enzymology* / Q000472:pathogenicity; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D014774:Virulence; D054311:nef Gene Products, Human Immunodeficiency Virus; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D015693:Gene Products, nef; D054311:nef Gene Products, Human Immunodeficiency Virus; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein