The dengue virus non-structural protein 1 (NS1) is secreted from mosquito cells in association with the intracellular cholesterol transporter chaperone caveolin complex

Dengue virus (DENV) is a mosquito-borne virus of the family Flaviviridae. The RNA viral genome encodes for a polyprotein that is co-translationally processed into three structural proteins and seven non-structural proteins. The non-structural protein 1 (NS1) is a multifunctional viral protein active...

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Bibliographic Details
Published inbioRxiv
Main Authors Romel Rosales Ramirez, Ludert, Juan E
Format Paper
LanguageEnglish
Published Cold Spring Harbor Cold Spring Harbor Laboratory Press 17.07.2018
Subjects
Brefeldin A
Caveolin
Caveolin-1
Chaperones
Cholesterol
Cyclosporins
Dengue fever
Genomes
Golgi apparatus
Localization
Mosquitoes
Proteins
Ribonucleic acid
RNA
Secretion
siRNA
Structural proteins
Virions
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Summary:Dengue virus (DENV) is a mosquito-borne virus of the family Flaviviridae. The RNA viral genome encodes for a polyprotein that is co-translationally processed into three structural proteins and seven non-structural proteins. The non-structural protein 1 (NS1) is a multifunctional viral protein actively secreted in vertebrate and mosquito cells during DENV infection. In mosquito cells, NS1 is secreted in a caveolin-1 (CAV-1) dependent manner by an unconventional pathway. The caveolin chaperone complex (CCC) is a cytoplasmic complex formed by caveolin-1 and the chaperones FKBP52, Cy40 and CyA which is responsible for cholesterol traffic inside the cell. In this work, we demonstrate that in infected mosquito cells, DENV NS1 is secreted by an early and unconventional route that bypasses the Golgi apparatus in close association with the CCC. Treatment of mosquito cells with classic secretion inhibitors such as brefeldin A, golgicide A and Fli-06 showed no effect on NS1 secretion, but significant reductions in recombinant luciferase secretion and virion release. Silencing the expression of CAV1, FKBP52 with siRNAs or the inhibition of CyA by cyclosporine A resulted in significant decrease in NS1 secretion without affecting virion release. Using co-localization, co-inmunoprecipitation and proximity ligation assays, NS1 was found to co-localize and interact with all the protein components of the CCC in mosquito infected cells. In addition, CAV-1 and FKBP52 expression was found augmented in DENV infected cells. Finally, the treatment of ZIKV infected mosquito cells with brefeldin A and golgicide A showed no effect on NS1 secretion, while affecting virion release. ZIKV NS1 was also found to co-localize with CAV-1 in infected mosquito cells. These results suggest that in mosquito cells, ZIKV NS1 follows the same secretory pathway observed for DENV NS1. The association of NS1 with the cholesterol transporter CCC agrees with the lipoprotein nature of secreted hexameric NS1.
DOI:10.1101/370932