Characterization of aggregate/aggresome structures formed by polyhedrin of Bombyx mori nucleopolyhedrovirus

Bombyx mori RPL13 participates in UV-induced DNA damage repair of B. mori nucleopolyhedrovirus through interaction with Bm65

Ribosomal protein L13 (RPL13) is highly conserved in evolution. At present, the properties and functions of RPL13 have not been characterised in insects. In this study, Bombyx mori RPL13 (BmRPL13) was first found to be specifically recruited to the sites of ultraviolet (UV)-induced DNA damage and contributed to UV damage repair. Escherichia coli expressing BmRPL13 showed better resistance to UV radiation. After knocking down the expression of BmRPL13 in BmN cells, the repair speed of UV-damaged DNA slowed down. The further results showed that BmRPL13 interacted with B. mori nucleopolyhedrovirus (BmNPV) ORF65 (Bm65) protein to locate at the UV-induced DNA damage sites of BmNPV and helped repair UV-damaged viral DNA.

A comprehensive review of protein misfolding disorders, underlying mechanism, clinical diagnosis, and therapeutic strategies

INTRODUCTION

Proteins are the most common biological macromolecules in living system and are building blocks of life. They are extremely dynamic in structure and functions. Due to several modifications, proteins undergo misfolding, leading to aggregation and thereby developing neurodegenerative and systemic diseases. Understanding the pathology of these diseases and the techniques used to diagnose them is therefore crucial for their effective management . There are several techniques, currently being in use to diagnose them and those will be discussed in this review.

AIM/OBJECTIVES

Current review aims to discuss an overview of protein aggregation and the underlying mechanisms linked to neurodegeneration and systemic diseases. Also, the review highlights protein misfolding disorders, their clinical diagnosis, and treatment strategies.

METHODOLOGY

Literature related to neurodegenerative and systemic diseases was explored through PubMed, Google Scholar, Scopus, and Medline databases. The keywords used for literature survey and analysis are protein aggregation, neurodegenerative disorders, Alzheimer's disease, Parkinson's disease, systemic diseases, protein aggregation mechanisms, etc. DISCUSSION /CONCLUSION: This review summarises the pathogenesis of neurodegenerative and systemic disorders caused by protein misfolding and aggregation. The clinical diagnosis and therapeutic strategies adopted for the management of these diseases are also discussed to aid in a better understanding of protein misfolding disorders. Many significant concerns about the role, characteristics, and consequences of protein aggregates in neurodegenerative and systemic diseases are not clearly understood to date. Regardless of technological advancements, there are still great difficulties in the management and cure of these diseases. Therefore, for better understanding, diagnosis, and treatment of neurodegenerative and systemic diseases, more studies to identify novel drugs that may aid in their treatment and management are required.

Cytoskeleton Protein BmACT1 Is Potential for the Autophagic Function and Nuclear Localization of BmAtg4b in Bombyx mori

Homologs of Autophagy-related (Atg) protein 4 are reported to cleave LC3 protein and facilitate autophagy occurrence differently in mammals, whereas their functions have not been investigated in insects. Three homologs, including BmAtg4a and its short form BmAtg4c as well as BmAtg4b, exist in Bombyx mori. Herein, the autophagic functions of BmAtg4a and BmAtg4b were investigated. qPCR detection found that BmAtg4a and BmAtg4b both peaked during larval-pupal metamorphosis when autophagy occurs robustly. Immunofluorescent staining showed that BmAtg4a was predominantly localized at the cytoplasm, while BmAtg4b had notable nuclear localization. Overexpression of BmAtg4a and BmAtg4b both slightly promoted basal autophagy but inhibited the autophagy induced by the infection of B. mori nucleopolyhedrovirus (BmNPV) and, thereby, its proliferation. In comparison, knockout of BmAtg4a or BmAtg4b significantly upregulated BmNPV-induced autophagy and its replication in BmN cells. Results of Co-immunoprecipitation associated with mass spectrum showed that the cytoskeleton protein B. mori actin A2 (BmACT2) and B. mori actin A1 (BmACT1) bound with BmAtg4a and BmAtg4b especially. Knockout of BmACT1 and BmACT2 inhibited BmAtg4b- and BmAtg4a-induced autophagy, respectively; moreover, knockout of BmACT1 reduced the ratio of cells with nuclear BmAtg4b. Of note, BmAtg4a and BmAtg4b had physical interaction, and they had an inhibitory effect on mutual autophagic function. In this work, we provide new insights into the autophagy machinery in insects as well as its function in the proliferation of BmNPV.

The Mechanisms of Silkworm Resistance to the Baculovirus and Antiviral Breeding

Silkworm (Bombyx mori) is not only an economic insect but also a model organism for life science research. Bombyx mori nucleopolyhedrovirus (BmNPV) disease is a major infectious disease in the world's sericulture industry. The cocoon loss caused by this disease accounts for more than 60% of the total loss caused by all silkworm diseases. To date, there has been no effective solution for preventing and treating this disease. The most effective measure is to breed disease-resistant varieties. The quickest way to breed disease-resistant varieties is to apply genetic modification. However, this requires that we obtain disease resistance genes and know the mechanism of disease resistance. Since the discovery of disease-resistant resources in 1989, scholars in the sericulture industry around the world have been inspired to search for resistance genes. In the past two decades, with the help of multi-omics technologies, screening of resistance genes, gene localization, protein modification, virus-host interactions, etc., researchers have found some candidate genes that have been proposed to function at the cellular or individual level. Several disease-resistant varieties have been obtained and used in production through hybrid breeding, RNA interference, and genetic modification. This article summarizes and reviews the discovery of and research advances related to silkworm resistance to BmNPV. It is anticipated that the review will inspire scientific researchers to continue searching for disease resistance genes, clarify the molecular mechanism of silkworm disease resistance, and promote disease-resistant silkworm breeding.

Mechanism of autophagy induced by low concentrations of chlorantraniliprole in silk gland, Bombyx mori

Chlorantraniliprole (CAP) is widely used in the control of agricultural pests, and its residues can affect the formation of silkworm (Bombyx. mori) cocoon easily. To accurately evaluate the toxicity of CAP to silkworms and clarify the mechanism of its effect on silk gland function, we proposed a novel toxicity evaluation method based on the body weight changes after CAP exposure. We also analyzed the Ca²⁺-related ATPase activity, characterized energy metabolism and transcriptional changes about the autophagy key genes on the downstream signaling pathways. The results showed that after a low concentration of CAP exposed for 96 h, there were CAP residues in the silk glands of B. mori, the activities of Ca²⁺-ATPase and Ca²⁺-Mg²⁺-ATPase decreased significantly (P ≤ 0.01), and the activation of AMPK-related genes AMPK-α and AMPK-β were up-regulated by 6.39 ± 0.02-fold and 12.33 ± 1.06-fold, respectively, reaching a significant level (P ≤ 0.01)). In addition, the autophagy-related genes Atg1, Atg6, Atg5, Atg7, and Atg8 downstream AMPK were significantly up-regulated at 96 h (P ≤ 0.05). The results of immunohistochemistry and protein expression assay for autophagy marker Atg8 further confirmed the occurrence of autophagy. Overall, our results indicate that CAP exposure leads to autophagy in the silk gland of B. mori and affects their physiological functions, which provides guidance for the evaluation of toxicity of low concentration environmental CAP residues to insects.

Bombyx mori Flap endonuclease 1 correlates with the repair of ultraviolet-induced DNA damage

Solar ultraviolet radiation (UV) can cause DNA damage in microorganisms. Flap endonuclease 1 (FEN1) is a structure-specific nuclease and plays important roles in DNA replication and repair. At present, the properties and functions of FEN1 have not been characterized in detail in invertebrates such as Bombyx mori. In this study, Bombyx mori FEN1 (BmFEN1) was expressed in E. coli, and was shown to have nuclease activity that nonspecifically cleaved DNA in vitro. However, inside the cell, BmFEN1 did not cleave DNA randomly. Truncated BmFEN1 missing the nuclear localization signal (346-380 aa) still had the nuclease activity, but was no longer precisely localized to the sites of UV-induced DNA damage. It was further found that BmFEN1 favored the faster repair of UV-damaged DNA. The present study will provide a reference for further understanding the functions of BmFEN1 and UV-induced DNA damage repair mechanisms in insects.

Involvement of the neddylation modification system in Bombyx mori nucleopolyhedrovirus replication

Neddylation is a posttranslational modification that is similar to ubiquitination, and involved in some critical biological processes, such as DNA repair, transcription regulation, and ubiquitin-proteasome pathway. Recently, it was found that neddylation inhibitor MLN4924 has potent antiviral activity against human viruses including herpes simplex virus (HSV)-1, HSV-2, and influenza viruses. Here, we report that MLN4924 could dramatically and dose-dependently inhibits the propagation, formation of budding virus (BV) and occlusion body (OB) of a lepidopteran virus-Bombyx mori nucleopolyhedrovirus (BmNPV), impaired OB assembly. In addition, the neddylation modification protein NEDD8 is colocalized with aggresome and autophagosome. Our findings suggest that inhibiting neddylation could be an antibaculovirus strategy and MLN4924 may be used as candidate drug for that purpose.

BmNPV Orf 65 (Bm65) Is Identified as an Endonuclease Directly Facilitating UV-Induced DNA Damage Repair

Baculoviruses have been used as biopesticides for the control of Lepidoptera larvae. However, solar UV radiation reduces the activity of baculovirus. In this study, an UV endonuclease, Bm65, was found encoded in the genome of Bombyx mori nuclear polyhedrosis virus (BmNPV). Bm65 (the ortholog of AcMNPV orf79) was guided by a key nuclear localization signal to enter the nucleus and accumulated at UV-induced DNA damage sites. Subsequent results further showed that Bm65-mediated DNA damage repair was not the only UV damage repair pathway of BmNPV. BmNPV also used host DNA repair proteins to repair UV-induced DNA damage. In summary, these results revealed that Bm65 was very important in UV-induced DNA damage repair of BmNPV, and BmNPV repaired UV-damaged DNA through a variety of ways. IMPORTANCE Baculovirus biopesticides are environmentally friendly insecticides and specifically infect invertebrates. UV radiation from the sunlight greatly reduces the activity of baculovirus biopesticides. However, the molecular mechanisms of most baculoviruses to repair UV-induced DNA damage remain unclear. Nucleotide excision repair (NER) is a major DNA repair pathway that removes UV-induced DNA lesions. At present, there are few reports about the nucleotide excision repair pathway in viruses. Here, we showed for the first time that the baculovirus Bm65 endonuclease actually cleaved UV-damaged DNA. Meanwhile, we found that BmNPV used both viral-encoded enzymes and host DNA damage repair proteins to reverse UV-induced DNA damage. These results will provide a reference for the research of UV damage repair of other viruses.

Myosin motors on the pathway of viral infections

Molecular motors are microscopic machines that use energy from adenosine triphosphate (ATP) hydrolysis to generate movement. While kinesins and dynein are molecular motors associated with microtubule tracks, myosins bind to and move on actin filaments. Mammalian cells express several myosin motors. They power cellular processes such as endo- and exocytosis, intracellular trafficking, transcription, migration, and cytokinesis. As viruses navigate through cells, they may take advantage or be hindered by host components and machinery, including the cytoskeleton. This review delves into myosins' cell roles and compares them to their reported functions in viral infections. In most cases, the previously described myosin functions align with their reported role in viral infections, although not in all cases. This opens the possibility that knowledge obtained from studying myosins in viral infections might shed light on new physiological roles for myosins in cells. However, given the high number of myosins expressed and the variety of viruses investigated in the different studies, it is challenging to infer whether the interactions found are specific to a single virus or can be applied to other viruses with the same characteristics. We conclude that the participation of myosins in viral cycles is still a largely unexplored area, especially concerning unconventional myosins.

Recombinant Protein Production and Purification of Insoluble Proteins

Proteins are synthesized in heterologous systems because of the impossibility to obtain satisfactory yields from natural sources. The efficient production of soluble and functional recombinant proteins is among the main goals in the biotechnological field. In this context, it is important to point out that under stress conditions, protein folding machinery is saturated and this promotes protein misfolding and, consequently, protein aggregation. Thus, the selection of the optimal expression organism and its growth conditions to minimize the formation of insoluble protein aggregates should be done according to the protein characteristics and downstream requirements. Escherichia coli is the most popular recombinant protein expression system despite the great development achieved so far by eukaryotic expression systems. Besides, other prokaryotic expression systems, such as lactic acid bacteria and psychrophilic bacteria, are gaining interest in this field. However, it is worth mentioning that prokaryotic expression system poses, in many cases, severe restrictions for a successful heterologous protein production. Thus, eukaryotic systems such as mammalian cells, insect cells, yeast, filamentous fungus, and microalgae are an interesting alternative for the production of these difficult-to-express proteins.

Viral Induced Protein Aggregation: A Mechanism of Immune Evasion

Various intrinsic and extrinsic factors can interfere with the process of protein folding, resulting in protein aggregates. Usually, cells prevent the formation of aggregates or degrade them to prevent the cytotoxic effects they may cause. However, during viral infection, the formation of aggregates may serve as a cellular defense mechanism. On the other hand, some viruses are able to exploit the process of aggregate formation and removal to promote their replication or evade the immune response. This review article summarizes the process of cellular protein aggregation and gives examples of how different viruses exploit it. Particular emphasis is placed on the ribonucleotide reductases of herpesviruses and how their additional non-canonical functions in viral immune evasion are closely linked to protein aggregation.

Deacetylation of HSC70-4 Promotes Bombyx mori Nucleopolyhedrovirus Proliferation via Proteasome-Mediated Nuclear Import

Silkworm (Bombyx mori) is a model organism with great agricultural economic value that plays a crucial role in biological studies. B. mori nucleopolyhedrovirus (BmNPV) is a major viral pathogen found in silkworms, which leads to huge silk loss annually. In a recent lysine acetylome of silkworm infected with BmNPV, we focused on the heat shock cognate protein 70-4 (HSC70-4) lysine acetylation change due to the consequent nuclear accumulation and viral structure assembly. In this study, the genome replication, proliferation, and production of budded viruses (BVs) were arrested by HSP/HSC70 inhibitor treatment. However, HSC70-4 overexpression enhanced BmNPV reproduction. Furthermore, site-direct mutagenesis for acetylated mimic (K/Q) or deacetylated mimic (K/R) mutants of HSC70-4 demonstrated that lysine 77 (K77) deacetylation promotes HSC70-4 stability, viral DNA duplication, and HSC70-4 nuclear entry upon BmNPV challenge, and the nuclear propulsion of HSC70-4 after viral stimulus might be dependent on the interaction with the carboxyl terminus of HSC70-interacting protein (CHIP, an E3 ubiquitin ligase), followed by ubiquitin-proteasome system assistance. In this study, single lysine 77 deacetylation of HSC70-4 was deemed a part of the locomotive pathway for facilitating BmNPV proliferation and provided novel insights into the antiviral strategic development.

Expression profile analysis of circular RNAs in BmN cells (Bombyx mori) upon BmNPV infection

The disease caused by Bombyx mori nucleopolyhedrovirus (BmNPV) has always been difficult to control, resulting in tremendous economic losses in the sericulture industry. Although much has been learned about the impact of noncoding RNAs on pathogenesis, the role of circular RNA (circRNA) in insect immunity remains unclear. To explore circRNA regulation involved in BmNPV infection, we used transcriptome analysis of BmN cells with or without BmNPV infection to generate circRNA data set. A total of 444 novel circRNAs were identified in BmN cells, with 198 pervasively distributed both in the control group and BmNPV-infection group. The host genes were enriched inMAPK signaling pathway, dorso-ventral axis formation, and ECM-receptor interaction, which were required for the normal larval growth. A total of 75 circRNAs were differentially expressed (DE) on BmNPV infection. Six downregulated circRNAs were validated by Sanger sequencing and qRT-PCR. DEcircRNA-miRNA-DEmRNA network was constructed based on the six validated circRNAs. Pathway analysis indicated that the predicted target genes were mainly enriched in the metabolic pathway and immune-related signaling pathway. Our results may provide a basis for further studies on circRNA function in BmN cells challenged by BmNPV infection and offer an insight into the molecular mechanism on silkworm-virus interaction.

Evidence for lysosomal biogenesis proteome defect and impaired autophagy in preeclampsia

The etiology of preeclampsia (PE), a serious pregnancy complication, remains an enigma. We have demonstrated that proteinopathy, a pathologic feature of neurodegenerative diseases, is a key observation in the placenta and serum from PE patients. We hypothesize that the macroautophagy/autophagy machinery that mediates degradation of aggregated proteins and damaged organelles is impaired in PE. Here, we show that TFEB (transcription factor EB), a master transcriptional regulator of lysosomal biogenesis, and its regulated proteins, LAMP1, LAMP2, and CTSD (cathepsin D), were dysregulated in the placenta from early and late onset PE deliveries. Primary human trophoblasts and immortalized extravillous trophoblasts (EVTs) showed reduced TFEB expression and nuclear translocation as well as lysosomal protein content in response to hypoxia. Hypoxia-exposed trophoblasts also showed decreased PPP3/calcineurin phosphatase activity and increased XPO1/CRM1 (exportin 1), events that inhibit TFEB nuclear translocation. These proteins were also dysregulated in the PE placenta. These results are supported by observed lysosomal ultrastructural defects with decreased number of autolysosomes in hypoxia-treated primary human trophoblasts. Autophagy-deficient human EVTs exhibited poor TFEB nuclear translocation, reduced lysosomal protein expression and function, and increased MTORC1 activity. Sera from PE patients induced these features and protein aggregation in EVTs. Importantly, trophoblast-specific conditional atg7 knockout mice exhibited reduced TFEB expression with increased deposition of protein aggregates in the placenta. These results provide compelling evidence for a regulatory link between accumulation of protein aggregates and TFEB-mediated impaired lysosomal biogenesis and autophagy in the placenta of PE patients. Abbreviation:atg7: autophagy related 7; CTSD: cathepsin D; ER: endoplasmic reticulum; EVTs: extravillous trophoblasts; KRT7: keratin 7; LAMP1: lysosomal associated membrane protein 1; LAMP2: lysosomal associated membrane protein 2; mSt: mStrawberry; MTORC1: mechanistic target of rapamycin complex 1; NP: normal pregnancy; NPS: normal pregnancy serum; PE: preeclampsia; PES: preeclampsia serum; p-RPS6KB: phosphorylated ribosomal protein S6 kinase B1; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TFEB: transcription factor EB; XPO1/CRM1: exportin 1.

BmNPV infection correlates with the enhancement of the resistance of Bombyx mori cells to UV radiation

At present, the effect of ultraviolet (UV) radiation on the interaction between Bombyx mori nucleopolyhedrovirus (BmNPV) and host remains unclear. In the current study, UV treatment significantly reduced the activity of BmNPV budded viruses (BVs), and UV-damaged BmN cells were not conducive to BmNPV proliferation. BmNPV infection significantly reduced the viability of host cells, but increased the viability of high-dose UV-treated host cells. Furthermore, the quantitative reverse-transcription PCR (qPCR) results suggested that BmNPV and Bombyx mori might mutually use the same DNA repair proteins for repairing UV-induced damage and BmNPV infection promote the ability of host cells to repair UV-induced damage.

Essential function of VCP/p97 in infection cycle of the nucleopolyhedrovirus AcMNPV in Spodoptera frugiperda Sf9 cells

The protein VCP/p97 (also named CDC48 and TER94) belongs to a type II subfamily of the AAA+ATPases and controls cellular proteostasis by acting upstream of proteasomes in the ubiquitin-proteasome protein degradation pathway. The function of VCP/p97 in the baculovirus infection cycle in insect cells remains unknown. Here, we identified VCP/p97 in the fall armyworm Spodoptera frugiperda (Sf9) cells and analyzed the replication of the Autographa californica multiple nucleopolyhedrovirus, AcMNPV, in Sf9 cells in which the VCP/p97 function was inhibited. The specific allosteric inhibitor of the VCP/p97 ATPase activity, NMS-873, did not deplete VCP/p97 in infected cells but caused a dose-dependent inhibition of viral DNA synthesis and efficiently suppressed expression of viral proteins and production of budded virions. NMS-873 caused accumulation of ubiquitinated proteins in a manner similar to the inhibitor of proteasome activity, Bortezomib. This suggests the essential function of VCP/p97 in the baculovirus infection cycle might be associated, at least in part, with the ubiquitin-proteasome system.

Discovery of anti-viral molecules and their vital functions in Bombyx mori

The silkworm Bombyx mori (B. mori), a lepidopteran model organism, has become an important model for molecular biology researches with its genome completely sequenced. Silkworms confront different types of virus diseases, mainly including those caused by Bombyx mori nucleopolyhedrovirus (BmNPV), Bombyx mori densovirus type 1 (BmDNV-1), Bombyx mori bidesovirus (BmBDV) which was termed as Bombyx mori densovirus type 2 (BmDNV-2) or Bombyx mori parvo-like virus (BmPLV) before in sericulture. B. mori offers excellent models to study the molecular mechanisms of insect innate immune responses to viruses. A variety of molecules and pathways have been identified to be involved in the immune responses in the silkworm to viruses, such as the antimicrobial peptides, prophenoloxidase-activating system, apoptosis, ROS, small RNA and related molecules. Here in this review, we summarize the current research advances in molecules involved in silkworm anti-virus pathways. Moreover, taking BmNPV as an example, we proposed a schematic model of molecules and pathways involved in silkworm immune responses against virus infection. We hope this review can facilitate further study of antiviral mechanisms in silkworm, and provide a reference for virus diseases in other organisms.

Bombyx mori Nuclear Polyhedrosis Virus (BmNPV) Induces Host Cell Autophagy to Benefit Infection

Bombyx mori nuclear polyhedrosis virus (BmNPV) is an important pathogen of silkworms. Despite extensive studies in recent decades, the interaction between BmNPV and host cells is still not clearly understood. Autophagy is an intrinsic innate immune mechanism and it controls infection autonomously in virus-infected cells. In this study, we found that BmNPV infection could trigger autophagy, as demonstrated by the formation of autophagosomes, fluorescent Autophagy-related gene 8-Green Fluorescent Protein (ATG8-GFP) punctate, and lipidated ATG8. Meanwhile, autophagic flux increased significantly when monitored by the ATG8-GFP-Red Fluorescent Protein (RFP) autophagy tandem sensor and protein degradation of p62. In addition, almost all of the identified autophagy-related genes (Atgs) had been up-regulated post infection in mRNA levels. Then, we screened Atgs with the greatest fold-change during virus infection. Interestingly, all of the screened Atgs positively regulated the expression of virus genes. Further studies showed that Atg7 and Atg9 could contribute to the level of autophagy caused by viral infection. Our results demonstrated that BmNPV induced host cell autophagy to benefit its infection. These results offer insight into the complex interactions between virus and host cell, and viral pathogenesis.

Protein composition analysis of polyhedra matrix of Bombyx mori nucleopolyhedrovirus (BmNPV) showed powerful capacity of polyhedra to encapsulate foreign proteins

Polyhedra can encapsulate other proteins and have potential applications as protein stabilizers. The extremely stable polyhedra matrix may provide a platform for future engineered micro-crystal devices. However, the protein composition of the polyhedra matrix remains largely unknown. In this study, the occlusion-derived virus (ODV)-removed BmNPV polyhedra matrix fraction was subjected to SDS-PAGE and then an LC-ESI-MS/MS analysis using a Thermo Scientific Q Exactive mass spectrometer. In total, 28 host and 91 viral proteins were identified. The host components were grouped into one of six categories, i.e., chaperones, ubiquitin and related proteins, host helicases, cytoskeleton-related proteins, RNA-binding proteins and others, according to their predicted Pfam domain(s). Most viral proteins may not be essential for polyhedra assembly, as evidenced by studies in the literature showing that polyhedra formation occurs in the nucleus upon the disruption of individual genes. The structural role of these proteins in baculovirus replication will be of significant interest in future studies. The immobilization of enhanced green fluorescent protein (eGFP) into the polyhedra by fusing with the C-terminus of BM134 that is encoded by open reading frame (ORF) 134 suggested that the polyhedra had a powerful capacity to trap foreign proteins, and BM134 was a potential carrier for incorporating proteins of interest into the polyhedra.

Evidence for the role of BmNPV Bm65 protein in the repair of ultraviolet-induced DNA damage

It is unclear how, or to what extent, baculovirus DNA that has been damaged by ultraviolet (UV) light is repaired during infection and replication. In our previous study, expression of Bombyx mori nucleopolyhedrovirus (BmNPV) ORF Bm65, a homolog of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac79, correlated with decreased inactivation of virus by UV irradiation. In the current study, we accumulated more evidence pointing to a role for Bm65 in repair of UV-induced DNA damage. The localization of Bm65 was studied using enhanced green fluorescent protein (EGFP) fusion constructs expressed in BmN cells transfected with a Bm65 expression plasmid. The results indicate that Bm65-EGFP accumulates in the nucleus. A host cell reactivation assay showed that Bm65 significantly increased the expression of UV-damaged mCherry reporter gene. An assay measuring cyclobutane pyrimidine dimers (CPDs) in UV-irradiated BmN cells found that CPD quantity was decreased in cells transfected with a Bm65 expression plasmid. We also showed that after UVC treatment, the viability of Bm65-transfected cells was higher than that of egfp-transfected cells. These results suggest that Bm65 may be involved in the repair of baculovirus DNA that has been damaged by UV light.

Identification and Characterization of BmVta1, a Bombyx mori (Lepidoptera: Bombycidae) Homologue for Vta1 That is Up-Regulated in Development

Vps20-associated 1 (Vta1) positively regulates Vacuolar protein sorting 4 (Vps4) to disassemble endosomal sorting complex required for transport III (ESCRT-III) for repeated uses in multivesicular body (MVB) pathway, virus budding and other processes. Currently, these proteins have mainly been studied in yeast and mammalian cells, while identities of them in insects remain largely unknown. We previously identified BmVps4, a Vps4 homologue from Bombyx mori. Here, we report the identification of a homologue for Vta1, designated as BmVta1. The BmVta1 cDNA contains an open reading frame of 933 bp and encodes a protein of 311 amino acid residues. We cloned BmVta1, expressed it in Escherichia coli, and prepared mouse polyclonal antibodies. Like BmVps4, BmVta1 is well conserved as shown by sequence analysis. Both proteins are localized in cytoplasm as revealed by subcellular location analysis. Interestingly, as revealed by semi-quantitative reverse transcription polymerase chain reaction (sqRT-PCR), transcriptions of BmVta1 and BmVps4 are highly up-regulated during silkworm metamorphosis and embryogenesis but down-regulated during larva stages, and are of higher levels in head, silk gland and testis than in Malpighian tube, fat body and ganglion, indicating important and similar roles of them in silkworm development and in silkworm tissues and organs. However, compared to BmVps4, the transcription of BmVta1 changes less drastically during development and is of much higher levels in midgut, ovary and hemolymph, suggesting the existence of distinct requirements of them in silkworm development and in certain tissues and organs.

Comparative Subcellular Proteomics Analysis of Susceptible and Near-isogenic Resistant Bombyx mori (Lepidoptera) Larval Midgut Response to BmNPV infection

The molecular mechanism of silkworm resistance to Bombyx mori nucleopolyhedrovirus (BmNPV) infection remains largely unclear. Accumulating evidence suggests that subcellular fractionation combined with proteomics is an ideal technique to analyse host antiviral mechanisms. To clarify the anti-BmNPV mechanism of the silkworm, the near-isogenic line BC9 (resistant strain) and the recurrent parent P50 (susceptible strain) were used in a comparative subcellular proteomics study. Two-dimensional gel electrophoresis (2-DE) combined with mass spectrometry (MS) was conducted on proteins extracted from the cytosol, mitochondria, and microsomes of BmNPV-infected and control larval midguts. A total of 87 proteins were successfully identified from the three subcellular fractions. These proteins were primarily involved in energy metabolism, protein metabolism, signalling pathways, disease, and transport. In particular, disease-relevant proteins were especially changed in microsomes. After infection with BmNPV, differentially expressed proteins (DEPs) primarily appeared in the cytosolic and microsomal fractions, which indicated that these two fractions might play a more important role in the response to BmNPV infection. After removing genetic background and individual immune stress response proteins, 16 proteins were identified as potentially involved in repressing BmNPV infection. Of these proteins, the differential expression patterns of 8 proteins according to reverse transcription quantitative PCR (RT-qPCR) analyses were consistent with the 2-DE results.

Subcellular localization of the five members of the human steroid 5α-reductase family

In humans the steroid 5α-reductase (SRD5A) family comprises five integral membrane enzymes that carry out reduction of a double bond in lipidic substrates: Δ⁴-3-keto steroids, polyprenol and trans-enoyl CoA. The best-characterized reaction is the conversion of testosterone into the more potent dihydrotestosterone carried out by SRD5A1-2. Some controversy exists on their possible nuclear or endoplasmic reticulum localization.

We report the cloning and transient expression in HeLa cells of the five members of the human steroid 5α-reductase family as both N- and C-terminus green fluorescent protein tagged protein constructs. Following the intrinsic fluorescence of the tag, we have determined that the subcellular localization of these enzymes is in the endoplasmic reticulum, upon expression in HeLa cells. The presence of the tag at either end of the polypeptide chain can affect protein expression and, in the case of trans enoyl-CoA reductase, it induces the formation of protein aggregates.

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All members of human testosterone 5α-reductase family were expressed in HeLa cells.

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Subcellular localization of SRD5A proteins in the endoplasmic reticulum is reported.

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The effect of GFP tagging at N- or C-term on SRD5A proteins expression was assessed.

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The TECRL gene is expressed for the first time and its product localizes in the ER.