Budding of Tiger Frog Virus (an Iridovirus) from HepG2 Cells via Three Ways Recruits the ESCRT Pathway

Abstract

The cellular endosomal sorting complex required for transport (ESCRT) pathway is a multifunctional pathway involved in cell physiological activities. While the majority of RNA viruses bearing L-domains are known to hijack the ESCRT pathway to complete the budding process, the budding of large and complex enveloped DNA viruses, especially iridoviruses, has been rarely investigated. In the present study, we use the tiger frog virus (TFV) as a model to investigate whether iridoviruses are released from host cells through the ESCRT pathway. Inhibition of class E proteins and auxiliary proteins (VPS4A, VPS4B, Tsg101, Alix, and Nedd4.1) reduces extracellular virion production, which preliminarily indicates that the ESCRT pathway is involved in TFV release. The respective interactions of TFV VP031L, VP065L, VP093L with Alix, Tsg101, Nedd4 suggest the underlying molecular mechanism by which TFV gets access to the ESCRT pathway. Co-depletion of Alix, Tsg101, and Nedd4.1 induces a significant reduction in extracellular virion production, which implies the functional redundancy of host factors in TFV budding. Those results are first observation that iridovirus gains access to ESCRT pathway through three ways of interactions between viral proteins and host proteins. Our study provides a better understanding of the budding mechanism of enveloped DNA viruses.

The E3 ubiquitin ligase NEDD4 mediates cell migration signaling of EGFR in lung cancer cells

“…Activated NEDD4 then is recruited to the EGFR-loaded endosomes (Fig. 2B ) or the ALIX/ESCRT vesicle transport machinery, as previous studies have shown [ 6 , 50 , 51 ]. On one hand, NEDD4 is collaborated with TNK2 (ACK1) to regulate transport of the EGFR-loaded endosomes to MVBs/lysosomes [ 13 , 38 ].…”

“…Early studies have shown that unconventional secretion of lysosomes is involved in cancer metastasis and cell migration and invasion [ 47 – 49 ], and NEDD4 participates in the ESCRT-dependent viral budding process, which resembles the MVB-dependent or the unconventional lysosomal secretion [ 50 , 51 ]. In addition, Rsp5p, the yeast homologue of NEDD4, directly regulates the ubiquitination-dependent sorting process of MVBs [ 6 ].…”

“…On one hand, NEDD4 is collaborated with TNK2 (ACK1) to regulate transport of the EGFR-loaded endosomes to MVBs/lysosomes [ 13 , 38 ]. On the other hand, the activated NEDD4 interacting with the endosomal EGFR or/and other signal proteins stimulates secretion of the lysosomal cathepsin B, most likely through regulation of the ESCRT complex for the membrane fusion between secretory lysosomes and plasma membrane, which resembles the process of viral budding mediated by NEDD4 [ 50 , 51 ]. In this proposed pathway, the NEDD4-dependent secretion of the lysosomal cathepsin B is a key step for lung cancer cell migration.…”

Identification of synthetic lethality based on a functional network by using machine learning algorithms

“…68 GO: 1903772 participates in the regulation of viral budding via the host endosomal sorting complex required for transport complex, thereby modulating the frequency, rate, or extent of viral budding. 69,70 Genes encoding the components of this complex, such as SKD1 and upstream LIP5 and IST1-LIKE1, are involved in specific synthetic lethal mechanisms. 71 The biological process of GO: 0003383 represents the actin-mediated contraction of the apical end of a polarized epithelial cell.…”

ALIX protein analysis: storage temperature may impair results

“…Indeed, several ALIX-associated bands have been observed upon immunoblot analysis when using protein lysates derived from either cultured cell lines or EVs [24 -29]. In some of these studies [24,25,27], ALIX appeared as two (or more) distinct bands, including a major one with the predicted molecular mass of approximately 93 kDa as well as additional bands with a smaller size. In other studies, although ALIX appeared as a single band with the expected molecular mass [26,28,29], the supplementary information (in which the respective uncropped blots are shown) revealed the presence of other band(s) which were not identified due to their surprising small molecular mass.…”