title: Graf1 Controls the Growth of Human Parainfluenza Virus Type 2 through Inactivation of RhoA Signaling.
abstract: Rho GTPases are involved in a variety of cellular activities and are regulated by guanine nucleotide exchange factors and GTPase-activating proteins (GAPs). We found that the activation of Rho GTPases by lysophosphatidic acid promotes the growth of human parainfluenza virus type 2 (hPIV-2). Furthermore, hPIV-2 infection causes activation of RhoA, a Rho GTPase. We hypothesized that Graf1 (also known as ARHGAP26), a GAP, regulates hPIV-2 growth by controlling RhoA signaling. Immunofluorescence analysis showed that hPIV-2 infection altered Graf1 localization from a homogenous distribution within the cytoplasm to granules. Graf1 colocalized with hPIV-2 P, NP, and L proteins. Graf1 interacts with P and V proteins via their N-terminal common region, and the C-terminal Src homology 3 domain-containing region of Graf1 is important for these interactions. In HEK293 cells constitutively expressing Graf1, hPIV-2 growth was inhibited, and RhoA activation was not observed during hPIV-2 infection. In contrast, Graf1 knockdown restored hPIV-2 growth and RhoA activation. Overexpression of hPIV-2 P and V proteins enhanced hPIV-2-induced RhoA activation. These results collectively suggested that hPIV-2 P and V proteins enhanced hPIV-2 growth by binding to Graf1 and that Graf1 inhibits hPIV-2 growth through RhoA inactivation.
  
  
  
  Robust growth of hPIV-2 requires Rho activation. hPIV-2 infection causes RhoA activation, which is suppressed by Graf1. Graf1 colocalizes with viral RNP (vRNP) in hPIV-2-infected cells. We found that Graf1 interacts with hPIV-2 P and V proteins. We also identified regions in these proteins which are important for this interaction. hPIV-2 P and V proteins enhanced the hPIV-2 growth via binding to Graf1, while Graf1 inhibited hPIV-2 growth through RhoA inactivation.
authors: Department of Microbiology, School of Medicine, Wakayama Medical University, Wakayam, Japan.
authors: Keisuke
authors: K
authors: Ohta
authors: Department of Microbiology, School of Medicine, Wakayama Medical University, Wakayam, Japan.
authors: Hideo
authors: H
authors: Goto
authors: Department of Microbiology, School of Medicine, Wakayama Medical University, Wakayam, Japan.
authors: Yusuke
authors: Y
authors: Matsumoto
authors: Department of Microbiology, School of Medicine, Wakayama Medical University, Wakayam, Japan.
authors: Natsuko
authors: N
authors: Yumine
authors: Department of Microbiology and Molecular Genetics, Mie University Graduate School of Medicine, Mie, Japan.
authors: Masato
authors: M
authors: Tsurudome
authors: Department of Microbiology, School of Medicine, Wakayama Medical University, Wakayam, Japan mnishio@wakayama-med.ac.jp.
authors: Machiko
authors: M
authors: Nishio
mesh_terms: D000818:Animals; D019556:COS Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism / Q000821:virology; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D010223:Parainfluenza Virus 2, Human / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014709:Vero Cells; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*; D018909:src Homology Domains / Q000502:physiology
chemical_list: D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein