CDC42 and Rac1 are implicated in the activation of the Nef-associated kinase and replication of HIV-1.
BACKGROUND
The negative factor (Nef) of human and simian immunodeficiency viruses (HIV-1, HIV-2 and SIV) is required for high levels of viremia and progression to AIDS. Additionally, Nef leads to cellular activation, increased viral infectivity and decreased expression of CD4 on the cell surface. Previously, we and others demonstrated that Nef associates with a cellular serine kinase (NAK) activity. Recently, it was demonstrated that NAK bears structural and functional similarity to p21-activated kinases (PAKs).


RESULTS
In this study, we demonstrate that Nef not only binds to but also activates NAK via the small GTPases CDC42 and Rac1. First, the dominant-negative PAK (PAKR), via its GTPase-binding domain, and dominant-negative GTPases (CDC42Hs-N17 and Rac1-N17) block the ability of Nef to associate with and activate NAK. Second, constitutively active small GTPases (CDC42Hs-V12 and Rac1-V12) potentiate the effects of Nef. Third, interactions between Nef and NAK result in several cellular effector functions, such as activation of the serum-response pathway. And finally, PAKR, CDC42Hs-N17 and Rac1-N17 decrease levels of HIV-1 production to those of virus from which the nef gene is deleted.


CONCLUSIONS
By activating NAK via small GTPases and their downstream effectors, Nef interacts with regulatory pathways required for cell growth, cytoskeletal rearrangement and endocytosis. Thus, NAK could participate in the budding of new virions, the modification of viral proteins and the increased endocytosis of surface molecules such as CD4. Moreover, blocking the activity of these GTPases could lead to new therapeutic interventions against AIDS.
Lu
X
X
Howard Hughes Medical Institute, University of California at San Francisco, California, USA.
Wu
X
X
Plemenitas
A
A
Yu
H
H
Sawai
E T
ET
Abo
A
A
Peterlin
B M
BM
D016475:3T3 Cells; D000818:Animals; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D015693:Gene Products, nef / Q000235:genetics* / Q000378:metabolism; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D026362:Serum Response Factor; D015398:Signal Transduction; D014779:Virus Replication; D020764:cdc42 GTP-Binding Protein; D054311:nef Gene Products, Human Immunodeficiency Virus; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D015693:Gene Products, nef; D009687:Nuclear Proteins; D026362:Serum Response Factor; D054311:nef Gene Products, Human Immunodeficiency Virus; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins