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

Abstract

11 12 Keywords: 13 dengue virus; zika virus; yellow fever virus; flavivirus; NS1; caveolin-1; chaperone caveolin 14 complex; viral protein trafficking; unconventional secretion; mosquito cells 15 16 17 ABSTRACT 18 Dengue virus (DENV) is a mosquito-borne virus of the family Flaviviridae. The RNA viral genome 19 encodes for a polyprotein that is co-translationally processed into three structural proteins and . CC-BY 4.0 International license is made available under aThe copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/370932 doi: bioRxiv preprint 2 20 seven non-structural proteins. The non-structural protein 1 (NS1) is a multifunctional viral protein 21 actively secreted in vertebrate and mosquito cells during DENV infection. In mosquito cells, NS1 22 is secreted in a caveolin-1 (CAV-1) dependent manner by an unconventional pathway. The 23 caveolin chaperone complex (CCC) is a cytoplasmic complex formed by caveolin-1 and the 24 chaperones FKBP52, Cy40 and CyA which is responsible for cholesterol traffic inside the cell. 25 In this work, we demonstrate that in infected mosquito cells, DENV NS1 is secreted by an early 26 and unconventional route that bypasses the Golgi apparatus in close association with the CCC.27 Treatment of mosquito cells with classic secretion inhibitors such as brefeldin A, golgicide A and 28 Fli-06 showed no effect on NS1 secretion, but significant reductions in recombinant luciferase 29 secretion and virion release. Silencing the expression of CAV1, FKBP52 with siRNAs or the 30 inhibition of CyA by cyclosporine A resulted in significant decrease in NS1 secretion without 31 affecting virion release. Using co-localization, co-inmunoprecipitation and proximity ligation 32 assays, NS1 was found to co-localize and interact with all the protein components of the CCC 33 in mosquito infected cells. In addition, CAV-1 and FKBP52 expression was found augmented in 34 DENV infected cells. Finally, the treatment of ZIKV infected mosquito cells with brefeldin A and 35 golgicide A showed no effect on NS1 secretion, while affecting virion release. ZIKV NS1 was 36 also found to co-localize with CAV-1 in infected mosquito cells. These results suggest that in 37 mosquito cells, ZIKV NS1 follows the same secretory pathway observed for DENV NS1. The 38 association of NS1 with the cholesterol transporter CCC agrees with the lipoprotein nature of 39 secreted hexameric NS1. 40 41 AUTHOR SUMMARY . CC-BY 4.0 International license is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/370932 doi: bioRxiv preprint 3 42 Dengue protein NS1 is secreted in infected mosquito and vertebrate cells. In humans, secreted 43 NS1 have been associated with pathogenesis. In mosquito cells, NS1 follows an unconventional 44 secretion pathway that is dependent on Caveolin-1. This work shows that in mosquito cells, NS1 45 secretion is associated to the chaperone caveolin complex, a...