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Gina M. Borgo

Bio: Gina M. Borgo is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Transduction (genetics) & Actin. The author has an hindex of 1, co-authored 3 publications receiving 12 citations.

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Journal ArticleDOI
TL;DR: The findings suggest that AC102 is necessary for nucleocapsid morphogenesis and actin assembly during late infection through its role as a component of the P78/83-C42-EC27-AC102 protein complex.
Abstract: The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV), the type species of alphabaculoviruses, is an enveloped DNA virus that infects lepidopteran insects and is commonly known as a vector for protein expression and cell transduction. AcMNPV belongs to a diverse group of viral and bacterial pathogens that target the host cell actin cytoskeleton during infection. AcMNPV is unusual, however, in that it absolutely requires actin translocation into the nucleus early in infection and actin polymerization within the nucleus late in infection coincident with viral replication. Of the six viral factors that are sufficient, when coexpressed, to induce the nuclear localization of actin, only AC102 is essential for viral replication and the nuclear accumulation of actin. We therefore sought to better understand the role of AC102 in actin mobilization in the nucleus early and late in infection. Although AC102 was proposed to function early in infection, we found that AC102 is predominantly expressed as a late protein. In addition, we observed that AC102 is required for F-actin assembly in the nucleus during late infection, as well as for proper formation of viral replication structures and nucleocapsid morphogenesis. Finally, we found that AC102 is a nucleocapsid protein and a newly recognized member of a complex consisting of the viral proteins EC27, C42, and the actin polymerization protein P78/83. Taken together, our findings suggest that AC102 is necessary for nucleocapsid morphogenesis and actin assembly during late infection through its role as a component of the P78/83-C42-EC27-AC102 protein complex.IMPORTANCE The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is an important biotechnological tool for protein expression and cell transduction, and related nucleopolyhedroviruses are also used as environmentally benign insecticides. One impact of our work is to better understand the fundamental mechanisms through which AcMNPV exploits the cellular machinery of the host for replication, which may aid in the development of improved baculovirus-based research and industrial tools. Moreover, AcMNPV's ability to mobilize the host actin cytoskeleton within the cell's nucleus during infection makes it a powerful cell biological tool. It is becoming increasingly clear that actin plays important roles in the cell's nucleus, and yet the regulation and function of nuclear actin is poorly understood. Our work to better understand how AcMNPV relocalizes and polymerizes actin within the nucleus may reveal fundamental mechanisms that govern nuclear actin regulation and function, even in the absence of viral infection.

15 citations

Posted ContentDOI
21 Oct 2021-bioRxiv
TL;DR: The role of a patatin-like phospholipase A2 enzyme (Pat1) during host cell infection by characterizing a Rickettsia parkeri mutant with a transposon insertion in the pat1 gene was investigated in this article.
Abstract: Spotted fever group Rickettsia species are arthropod-borne obligate intracellular bacteria that can cause mild to severe human disease. These bacteria invade host cells, replicate in the cell cytosol, and then spread from cell to cell. To access the host cytosol and avoid detection by immune surveillance mechanisms, these pathogens must have evolved efficient ways to escape membrane-bound vacuoles. Although Rickettsia are predicted to express factors that disrupt host membranes, little is known about how and when these proteins function during infection. Here, we investigated the role of a Rickettsia patatin-like phospholipase A2 enzyme (Pat1) during host cell infection by characterizing a Rickettsia parkeri mutant with a transposon insertion in the pat1 gene. We show that Pat1 is important for infection in a mouse model and in host cells. We further show that Pat1 is critical for efficiently escaping from the single and double membrane-bound vacuoles into the host cytosol, and for avoiding host galectins that mark damaged membranes. In the host cytosol, Pat1 is important for avoiding host polyubiquitin, preventing recruitment of autophagy receptor p62, and promoting actin-based motility and cell-cell spread. Our results show that Pat1 plays critical roles in escaping host membranes and promoting cell-cell spread during R. parkeri infection and suggest diverse roles for patatin-like phospholipases in facilitating microbial infection. ImportanceSpotted fever group Rickettsia are bacteria that reside in ticks and can be transmitted to mammalian hosts, including humans. Severe disease is characterized by high fever, headache, and rash, and results in occasional mortality despite available treatment. Rickettsia interact with host cell membranes while invading cells, escaping into the cytosol, and evading cellular defenses. Bacterial phospholipase enzymes have been proposed as critical factors for targeting host cell membranes, however the specific roles of rickettsial phospholipases are not well defined. We investigated the contribution of one conserved patatin-like phospholipase, Pat1, in Rickettsia parkeri. We observed that Pat1 is important for virulence in an animal model. Moreover, Pat1 plays critical roles in host cells by facilitating access to the cell cytosol, inhibiting detection by host defense pathways, and promoting cell-cell spread. Our study indicates that Pat1 performs several critical functions, suggesting a broad role for phospholipases throughout the Rickettsia lifecycle.

3 citations

Posted ContentDOI
19 Jan 2018-bioRxiv
TL;DR: The findings suggest that AC102 is necessary for nucleocapsid morphogenesis and actin assembly during late infection through its role as a component of the P78/83-C42-EC27-AC102 protein complex.
Abstract: The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV), the type species of alphabaculoviruses, is an enveloped DNA virus that infects lepidopteran insects and is commonly known as a vector for protein expression and cell transduction AcMNPV belongs to a diverse group of viral and bacterial pathogens that target the host cell actin cytoskeleton during infection AcMNPV is unusual, however, in that it absolutely requires actin translocation into the nucleus early in infection, and actin polymerization within the nucleus late in infection coincident with viral replication Of the six viral factors that are sufficient, when coexpressed, to induce the nuclear localization of actin, only AC102 is essential for viral replication and the nuclear accumulation of actin We therefore sought to better understand the role of AC102 in actin mobilization in the nucleus early and late in infection Although AC102 was thought to function early in infection, we found that AC102 is predominantly expressed as a late protein In addition, we observed that AC102 is required for F-actin assembly in the nucleus during late infection, as well as for proper formation of viral replication structures and nucleocapsid morphogenesis Finally, we found that AC102 is a nucleocapsid protein and a newly recognized member of a complex consisting of the viral proteins EC27, C42, and the actin polymerization protein P78/83 Taken together, our findings suggest that AC102 is necessary for nucleocapsid morphogenesis and actin assembly during late infection through its role as a component of the P78/83-C42-EC27-AC102 protein complex

2 citations


Cited by
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TL;DR: In this paper, the authors applied both affinity purification mass spectrometry (AP-MS) and the complementary proximity-based labeling method (BioID-MS), to map the interactions relevant to viral processing.
Abstract: Treatment options for COVID-19, caused by SARS-CoV-2, remain limited. Understanding viral pathogenesis at the molecular level is critical to develop effective therapy. Some recent studies have explored SARS-CoV-2-host interactomes and provided great resources for understanding viral replication. However, host proteins that functionally associate with SARS-CoV-2 are localized in the corresponding subnetwork within the comprehensive human interactome. Therefore, constructing a downstream network including all potential viral receptors, host cell proteases, and cofactors is necessary and should be used as an additional criterion for the validation of critical host machineries used for viral processing. This study applied both affinity purification mass spectrometry (AP-MS) and the complementary proximity-based labeling MS method (BioID-MS) on 29 viral ORFs and 18 host proteins with potential roles in viral replication to map the interactions relevant to viral processing. The analysis yields a list of 693 hub proteins sharing interactions with both viral baits and host baits and revealed their biological significance for SARS-CoV-2. Those hub proteins then served as a rational resource for drug repurposing via a virtual screening approach. The overall process resulted in the suggested repurposing of 59 compounds for 15 protein targets. Furthermore, antiviral effects of some candidate drugs were observed in vitro validation using image-based drug screen with infectious SARS-CoV-2. In addition, our results suggest that the antiviral activity of methotrexate could be associated with its inhibitory effect on specific protein-protein interactions.

27 citations

Journal ArticleDOI
TL;DR: These studies identified gene expression patterns associated with ODV-mediated infection of the midgut in Trichoplusia ni and compared those results with prior results from BV-infected cultured cells, which simulate secondary infection, and identified specific viral strategies to overcome or avoid host defenses in the gut and rapidly move infection from the midGut, into the hemocoel to facilitate systemic infection.
Abstract: The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a large double-stranded DNA (dsDNA) virus that encodes approximately 156 genes and is highly pathogenic to a variety of larval lepidopteran insects in nature. Oral infection of larval midgut cells is initiated by the occlusion-derived virus (ODV), while secondary infection of other tissues is mediated by the budded virus (BV). Global viral gene expression has been studied in detail in BV-infected cell cultures, but studies of ODV infection in the larval midgut are limited. In this study, we examined expression of the ∼156 AcMNPV genes in Trichoplusia ni midgut tissue using a transcriptomic approach. We analyzed expression profiles of viral genes in the midgut and compared them with profiles from a T. ni cell line (Tnms42). Several viral genes (p6.9, orf76, orf75, pp31, Ac-bro, odv-e25, and odv-ec27) had high expression levels in the midgut throughout the infection. Also, the expression of genes associated with occlusion bodies (polh and p10) appeared to be delayed in the midgut in comparison with the cell line. Comparisons of viral gene expression profiles revealed remarkable similarities between the midgut and cell line for most genes, although substantial differences were observed for some viral genes. These included genes associated with high level BV production (fp-25k), acceleration of systemic infection (v-fgf), and enhancement of viral movement (arif-1/orf20). These differential expression patterns appear to represent specific adaptations for virus infection and transmission through the polarized cells of the lepidopteran midgut.IMPORTANCE Baculoviruses such as AcMNPV are pathogens that are natural regulators of certain insect populations. Baculovirus infections are biphasic, with a primary phase initiated by oral infection of midgut epithelial cells by occlusion-derived virus (ODV) virions and a secondary phase in which other tissues are infected by budded-virus (BV) virions. While AcMNPV infections in cultured cells have been studied extensively, comparatively little is known regarding primary infection in the midgut. In these studies, we identified gene expression patterns associated with ODV-mediated infection of the midgut in Trichoplusia ni and compared those results with prior results from BV-infected cultured cells, which simulate secondary infection. These studies provide a detailed analysis of viral gene expression patterns in the midgut, which likely represent specific viral strategies to (i) overcome or avoid host defenses in the gut and (ii) rapidly move infection from the midgut, into the hemocoel to facilitate systemic infection.

23 citations

Journal ArticleDOI
TL;DR: This study demonstrated that the alphabaculovirus AcMNPV exhibited actin- and microtubule-dependent transport for nucleocapsid release predominantly from within early endosomes, implying that AcM NPV exhibits cell type specificity in the requirement of the cytoskeleton network.
Abstract: The budded virus of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) infects insect cells through mainly clathrin-mediated endocytosis. However, the cell entry pathway of AcMNPV remains unclear. In this study, by using population-based analysis of single-virus tracking and electron microscopy, we investigated the internalization, fusion behavior, and endocytic trafficking of AcMNPV. AcMNPV internalization into host insect cells was facilitated by actin polymerization and dynamin. After incorporation into early endosomes, the AcMNPV envelope fused with the membranes of early endosome, allowing for nucleocapsid release into the cytoplasm. Microtubules were implicated in the bidirectional and long-range transport of virus-containing endosomes. In addition, microtubule depolymerization reduced the motility of virus-bearing early endosomes, impairing the progression of infection beyond enlarged early endosomes. These findings demonstrated that AcMNPV internalization was facilitated by actin polymerization in a dynamin-dependent manner, and nucleocapsid release occurred in early endosomes in a microtubule-dependent manner. This study provides mechanistic and kinetic insights into AcMNPV infection and enhance our understanding of the infection pathway of baculoviruses.IMPORTANCE Baculoviruses are used widely as environmentally benign pesticides, protein expression systems, and potential mammalian gene delivery vectors. Despite the significant application value, little is known about the cell entry and endocytic trafficking pathways of baculoviruses. In this study, we demonstrated that the alphabaculovirus AcMNPV exhibited actin- and microtubule-dependent transport for nucleocapsid release predominantly from within early endosomes. In contrast to AcMNPV transduction in mammalian cells, its infection in host insect cells is facilitated by actin polymerization for internalization and microtubules for endocytic trafficking within early endosomes, implying that AcMNPV exhibits cell type specificity in the requirement of the cytoskeleton network. In addition, experimental depolymerization of microtubules impaired the progression of infection beyond enlarged early endosomes. This is the first study that dissects the cell entry pathway of baculoviruses in host cells at the single-particle level, which advances our understanding of the early steps of baculovirus entry.

13 citations

Journal ArticleDOI
TL;DR: In this chapter, research advances relating to key aspects of the baculovirus life cycle are reviewed, and the application of a newly-developed bacULovirus synthetic biology technology is introduced.
Abstract: Baculoviridae constitutes a family of insect-specific, large DNA viruses with a unique life cycle characterized by the production of two morphologically distinct virions, the budded virus (BV) and the occlusion-derived virus (ODV). ODV and BV, with different tissue tropisms, have been widely applied in the areas of biological control and biotechnology, respectively. In nature, baculovirus infection of susceptible host larvae is initiated by ODV-mediated primary infection, followed by the production of BV for spreading infection within larval body. Across millions of years of co-evolution with their hosts, baculoviruses have developed dedicated mechanisms for efficient entry/egress, genome replication/transcription, and virion assembly by employing either their own proteins or host machineries. They have also adopted versatile strategies to precisely regulate the immunity, behaviors and physiology of hosts to facilitate their own replication and dispersal. In this chapter, research advances relating to key aspects of the baculovirus life cycle are reviewed, and the application of a newly-developed baculovirus synthetic biology technology is introduced. Finally, future avenues for baculovirus research are discussed.

11 citations

Journal ArticleDOI
07 Nov 2019-Viruses
TL;DR: This review highlights the current knowledge about the nuclear trafficking of cellular proteins associated with viral propagation and some classical and non-classical NLSs have been identified in a number of viral proteins.
Abstract: Typical viral propagation involves sequential viral entry, uncoating, replication, gene transcription and protein synthesis, and virion assembly and release. Some viral proteins must be transported into host nucleus to facilitate viral propagation, which is essential for the production of mature virions. During the transport process, nuclear localization signals (NLSs) play an important role in guiding target proteins into nucleus through the nuclear pore. To date, some classical nuclear localization signals (cNLSs) and non-classical NLSs (ncNLSs) have been identified in a number of viral proteins. These proteins are involved in viral replication, expression regulation of viral genes and virion assembly. Moreover, other proteins are transported into nucleus with unknown mechanisms. This review highlights our current knowledge about the nuclear trafficking of cellular proteins associated with viral propagation.

6 citations