Zinc finger protein RP-8, the Bombyx mori ortholog of programmed cell death 2, regulates cell proliferation

NPC Intracellular Cholesterol Transporter 1 Regulates Ovarian Maturation and Molting in Female Macrobrachium nipponense

NPC intracellular cholesterol transporter 1 (NPC1) plays an important role in sterol metabolism and transport processes and has been studied in many vertebrates and some insects, but rarely in crustaceans. In this study, we characterized NPC1 from Macrobrachium nipponense (Mn-NPC1) and evaluated its functions. Its total cDNA length was 4283 bp, encoding for 1344 amino acids. It contained three conserved domains typical of the NPC family (NPC1_N, SSD, and PTC). In contrast to its role in insects, Mn-NPC1 was mainly expressed in the adult female hepatopancreas, with moderate expression in the ovary and heart. No expression was found in the embryo (stages CS-ZS) and only weak expression in the larval stages from hatching to the post-larval stage (L1-PL15). Mn-NPC1 expression was positively correlated with ovarian maturation. In situ hybridization showed that it was mainly located in the cytoplasmic membrane and nucleus of oocytes. A 25-day RNA interference experiment was employed to illustrate the Mn-NPC1 function in ovary maturation. Experimental knockdown of Mn-NPC1 using dsRNA resulted in a marked reduction in the gonadosomatic index and ecdysone content of M. nipponense females. The experimental group showed a significant delay in ovarian maturation and a reduction in the frequency of molting. These results expand our understanding of NPC1 in crustaceans and of the regulatory mechanism of ovarian maturation in M. nipponense.

Ribosomal Protein uS5 and Friends: Protein-Protein Interactions Involved in Ribosome Assembly and Beyond

Ribosomal proteins are fundamental components of the ribosomes in all living cells. The ribosomal protein uS5 (Rps2) is a stable component of the small ribosomal subunit within all three domains of life. In addition to its interactions with proximal ribosomal proteins and rRNA inside the ribosome, uS5 has a surprisingly complex network of evolutionarily conserved non-ribosome-associated proteins. In this review, we focus on a set of four conserved uS5-associated proteins: the protein arginine methyltransferase 3 (PRMT3), the programmed cell death 2 (PDCD2) and its PDCD2-like (PDCD2L) paralog, and the zinc finger protein, ZNF277. We discuss recent work that presents PDCD2 and homologs as a dedicated uS5 chaperone and PDCD2L as a potential adaptor protein for the nuclear export of pre-40S subunits. Although the functional significance of the PRMT3-uS5 and ZNF277-uS5 interactions remain elusive, we reflect on the potential roles of uS5 arginine methylation by PRMT3 and on data indicating that ZNF277 and PRMT3 compete for uS5 binding. Together, these discussions highlight the complex and conserved regulatory network responsible for monitoring the availability and the folding of uS5 for the formation of 40S ribosomal subunits and/or the role of uS5 in potential extra-ribosomal functions.

Peroxiredoxin 1 of Procambarus clarkii govern immune responses during pathogen infection

Members of the peroxiredoxin family are involved in a wide variety of physiological processes, including the ability to combat the effects of oxidative stress and immune responses, among others. Here, we cloned the cDNA of Procambarus clarkii Peroxiredoxin 1 (designated as PcPrx-1) and investigated its biological role in immune system functions in relation to microbial pathogens. The PcPrx-1 cDNA had 744 base pairs in an open reading frame that encoded 247 amino acid residues and contained a PRX_Typ2cys domain. The analysis of tissue specific expression patterns revealed that PcPrx-1 expression was ubiquitous in all tissues. In addition, the mRNA transcript of PcPrx-1 was found to be highest in the hepatopancreas. There was a significant upregulation of PcPrx-1 gene transcripts after exposure to LPS, PGN, and Poly I:C, but the transcription patterns were different after pathogen challenge. Double-stranded RNA was used to knockdown PcPrx-1, which resulted in a striking change in the expression of all the tested P. clarkii immune-associated genes, including lectin, Toll, cactus, chitinase, phospholipase, and sptzale. On the whole, these results suggest that PcPrx-1 is important to confer innate immunity against pathogens by governing the expression of critical transcripts that encode immune-associated genes.

The Potential Biological Roles of Circular RNAs in the Immune Systems of Insects to Pathogen Invasion

Circular RNAs (circRNAs) are a newly discovered class of endogenously expressed non-coding RNAs (ncRNAs). They are highly stable, covalently closed molecules that frequently exhibit tissue-specific expression in eukaryotes. A small number of circRNAs are abundant and have been remarkably conserved throughout evolution. Numerous circRNAs are known to play important biological roles by acting as microRNAs (miRNAs) or protein inhibitors ('sponges'), by regulating the function of proteins, or by being translated themselves. CircRNAs have distinct cellular functions due to structural and production differences from mRNAs. Recent advances highlight the importance of characterizing circRNAs and their targets in a variety of insect species in order to fully understand how they contribute to the immune responses of these insects. Here, we focus on the recent advances in our understanding of the biogenesis of circRNAs, regulation of their abundance, and biological roles, such as serving as templates for translation and in the regulation of signaling pathways. We also discuss the emerging roles of circRNAs in regulating immune responses to various microbial pathogens. Furthermore, we describe the functions of circRNAs encoded by microbial pathogens that play in their hosts.

Identification and the immunological role of two Nimrod family genes in the silkworm, Bombyx mori

In animals, immune signaling pathways and effector molecules participate in attenuating microbial infection. Recent work has shown that the Nimrod family proteins can directly bind to bacteria, and this binding leads to bacterial phagocytosis. Although the Nimrod gene family has been reported in many non-drosophilids, their functions remain unexplored in most insect species. Here, we report two members (Nimrod-B and Draper) of the Nimrod gene family from Bombyx mori and analyzed their role in immunity. The two genes were ubiquitously expressed in the tested tissues; but, they transcribed preferentially in immune tissues. The developmental profiles showed that BmNimrod-B and BmDraper transcription levels were highest in the pupal stages. Challenge with microbial pathogens induced the transcription levels of all two genes at different time points. Knockdown of BmDraper decreased the bacterial clearance and increased their replication relative to the control group, whereas, BmNimrod-B suppression had a non-significant effect on them. Furthermore, the mortality rate was increased after BmDraper silencing. The knockdown of these genes did not significantly affect the production of antimicrobial peptides following E. coli infection. Taken together, the Nimrod family genes play a crucial role in host defense by positively regulating the antibacterial immune response in silkworm B. mori.

Molecular characterization and functional analysis of the lysosomal cathepsin D-like gene in red swamp crayfish, Procambarus clarkii

Aspartic proteinases are one of the four families of proteinase enzymes that are widely present in living organisms. They are involved in various physiological events, such as protein degradation, development, and host defense. However, the characterization and functional roles of aspartic proteinases remain to be elucidated in crustaceans. Here, we characterized a fragment of cathepsin D-like cDNA from red swamp crayfish, Procambarus clarkii (Pc-cathepsin D-like). The open reading frame of the Pc-cathepsin D-like gene contained 1152 bp, encoding a protein of 383 amino acid residues. We also evaluated the immunological role of the Pc-cathepsin D-like gene in vivo. Spatial distribution analysis revealed that the Pc-cathepsin D-like mRNA was high in the hepatopancreas, followed by the gut, gills, and hemocytes of P. clarkii. The expression levels of the Pc-cathepsin D-like gene increased following challenge with viral (polyinosinic: polycytidylic acid) and bacterial (lipopolysaccharides, peptidoglycan) PAMPs compared with PBS injection. The suppression of the Pc-cathepsin D-like gene by RNA interference significantly increased the expression of immune-associated genes. These results showed that the Pc-cathepsin D-like gene has an essential biological role in innate immune responses because it regulates the expression of immune-associated genes.

Dietary Serine and Sulfate-Containing Amino Acids Related to the Nutritional Status of Selenium in Lactating Chinese Women

Previous studies suggested that serine can promote the synthesis of selenoproteins and the interaction, transformation, and replacement of serine, cysteine, and selenocysteine have been observed in the human body. This study was designed to clarify whether the dietary intakes of serine and sulfate-containing amino acids (SAAs) could directly affect the selenium (Se) nutritional status or the level of milk Se in lactating women. Breast milk and plasma samples were collected from a total of 264 lactating Chinese women when they revisited their local hospital at the 42nd day postpartum to detect the concentration of Se with ICP-MS and the content of selenoprotein P (SEPP1) and the activity of glutathione peroxidase 3 (GPX3) in the plasma by ELISA. The daily Se intake by each subject was calculated based on her own plasma Se concentration. The 24-h dietary record data for 3 consecutive days were collected to calculate their dietary intakes of protein together with each amino acid daily based on the China Food Composition Tables (CFCT). Ordinal polytomous logistic regression was applied to examine the determinants of BMI values for lactating women. For all subjects, the concentration of plasma SEPP1 and milk Se of participants with insufficient Se intake were significantly associated with the dietary intake of serine and 2 SAAs (methionine and cystine), respectively (P < 0.05). No significant correlation was found between each amino acid related to the synthesis of endogenous serine and every biomarker of the Se nutrition status in subjects with an insufficient dietary protein intake (P > 0.05). The ordinal logistic regression analysis showed that dietary protein intake (ordinal OR 1.012, 95% CI = 0.004-0.020, P = 0.002) and plasma SEPP1 (ordinal OR 0.988, 95% CI = - 0.023 to - 0.001, P = 0.036) affected the BMI value together in these lactating women. In conclusion, dietary serine and SAAs were found to directly affect the nutritional status, and both high protein intake and low plasma SEPP1 might be the health risks in these lactating Chinese women.

Bmintegrin β1: A broadly expressed molecule modulates the innate immune response of Bombyx mori

Integrins are transmembrane glycoproteins that are broadly distributed in living organisms. As a heterodimer, they contain an α and a β subunit, which are reported to be associated with various physiological and pathological processes. In the present study, a 2502 bp full-length cDNA sequence of Bmintegrin β1 was obtained from the silkworm, Bombyx mori. Bmintegrin β1 belongs to the β subunit of the integrin family and contains several typical structures of integrins. Gene expression profile analysis demonstrated that Bmintegrin β1 was ubiquitously expressed in all tested tissues and organs, with the maximum expression levels in fat body and hemocytes. The immunofluorescence results showed that Bmintegrin β1 was located in the cell membrane and widely distributed in fat bodies and different types of hemocytes. Bmintegrin β1 expression was remarkably increased after challenging with different kinds of bacteria and pathogen-associated molecular patterns (PAMPs). Further investigation revealed that Bmintegrin β1 could participate in the agglutination of pathogenic bacteria possibly through direct binding with the relative bacteria and PAMPs. Altogether, this study provides a novel insight into the immune functional features of Bmintegrin β1.

Molecular characterization of a heat shock protein 21 (Hsp21) from red swamp crayfish, Procambarus clarkii in response to immune stimulation

Small heat shock proteins are a molecular chaperone and implicated in various physiological and stress processes in animals. However, the immunological functions of Hsp genes remain to elucidate in the crustaceans, particularly in red swamp crayfish, Procambarus clarkii. Here we report the cloning of heat shock protein 21 from the P. clarkii (hereafter Pc-Hsp21). The open reading frame of Pc-Hsp21 was 555 base pairs, encoding a protein of 184 amino acid residues with an alpha-crystallin family domain. Quantitative real-time PCR (qRT-PCR) analysis revealed a constitutive transcript expression of Pc-Hsp21 in the tested tissue, with the highest in hepatopancreas. The transcript abundance for this gene enhanced in hepatopancreas following immune challenge with the lipopolysaccharide, peptidoglycan, and poly I:C compared to the control group. The depletion of Pc-Hsp21 by double-stranded RNA altered transcript expression profiles of several genes in hepatopancreas, genes involved in the crucial immunological pathways of P. clarkii. These results suggest that Pc-Hsp21 plays an essential biological role in the microbial stress response by modulating the expression of immune-related genes in P. clarkii.

Characterization of the cathepsin D in Procambarus clarkii and its biological role in innate immune responses

Cathepsin D belongs to aspartic protease family, produced in the rough endoplasmic reticulum, and then transported to lysosomes, where it participates in various physiological processes. Despite its importance, only a few reports available on the functional role of cathepsin D in crustaceans. Herein, we cloned a cDNA fragment of cathepsin D from the hepatopancreas of the red swamp crayfish, Procambarus clarkii (Pc-cathepsin D) for the first time. It included 1158 base pairs open reading frame, encoding a protein of 385 amino acids. Multiple alignment analysis confirmed the presence of aspartic proteinase active sites and N glycosylation sites. Pc-cathepsin D mRNA expression was high in the gills followed by gut, heart, hepatopancreas of P. clarkii. At different time points post-infection with lipopolysaccharides, peptidoglycan, or polyinosinic polycytidylic acid, Pc-cathepsin D mRNA expression significantly enhanced compared with the control group. Knockdown of the Pc-cathepsin D by double-stranded RNA, strikingly, changed the expression of all the tested P. clarkii immune-associated genes, including Pc-Toll, Pc-lectin, Pc-cactus, Pc-anti-lipopolysaccharide factor, Pc-phospholipase, and Pc-sptzale. Altogether, these results suggest that Pc-cathepsin D is needed to confer innate immunity against microbial pathogens by modulating the expression of crucial transcripts that encode immune-associated genes.

Heat shock protein 20 from Procambarus clarkii is involved in the innate immune responses against microbial infection

Small heat shock proteins (shsps) are conserved across invertebrate species. They are implicated in the modulation of various biological processes, such as immune responses, abiotic stress tolerance metamorphosis, and embryonic development. Herein, we identified a heat shock protein 20 from the red swamp crayfish, Procambarus clarkii (named as Pc-Hsp20), and performed in vivo studies to elucidate its physiological functions in the innate immunity. The open reading frame of Pc-Hsp20 was 609 base pair, encoding a protein of 202 amino acid residues with a hsp20/alpha crystallin family domain. Pc-Hsp20 was ubiquitously expressed in various tissues; however, it was highest in the hepatopancreas. The challenge with immune elicitors remarkably enhanced the transcript level of Pc-Hsp20 in the hepatopancreas when compared with the control. Administration of double-stranded RNA could significantly reduce expression of the Pc-Hsp20 mRNAs, and most of the immune-related genes expression enhanced with a variable concentration in the hepatopancreas. Altogether, these results suggest that Pc-Hsp20 may participate in innate immunity against microbial pathogens.

The red swamp crayfish, Procambarus clarkii cathepsin C, participates in the innate immune response to the viral and bacterial pathogens

The cathepsin C, a lysosomal cysteine protease, involves the modulation of immune and inflammatory responses in living organisms. However, the knowledge on cathepsin C in red swamp crayfish (Procambarus clarkii), a freshwater crustacean with economic values, remained unclear. In the present study, we provide identification and molecular characterization of cathepsin C from P. clarkii. (Hereafter Pc-cathepsin C). The Pc-cathepsin C cDNA contained a 1356 bp open reading frame that encoded a protein of 451 amino acid residues. The deduced amino acid sequence comprised of cathepsin C exclusion domain and pept_C1 domain, and also catalytic residues (Cys²⁴⁸, His³⁹⁵ and Asn⁴¹⁷). Analysis of the transcriptional patterns of the Pc-cathepsin C gene revealed that it was broadly distributed in various tissues of P. clarkii, and it was more abundant in the hepatopancreas and gut. Following a challenge with viral and bacterial pathogen-associated molecular patterns, the expression of Pc-cathepsin C was strongly enhanced at different time points. The knockdown of Pc-cathepsin C, altered the expression of immune-responsive genes, suggesting its immunoregulatory role in P. clarkii. This study has identified and provided the immunoregulatory function of Pc-cathepsin C, which will contribute to further investigation of the molecular mechanism of cathepsin C in crustaceans.

Suppressors of cytokine signaling proteins as modulators of development and innate immunity of insects

The suppressors of cytokine signaling (SOCS) are a family of intracellular molecules. Many members of this family have been reported to be involved in various physiological processes in invertebrates and vertebrates (e.g., developmental process and immune response). The functions of SOCS molecules seem to remain conserved in animals throughout evolutionary history. The members of the SOCS family play vital roles in the physiological processes by regulating the extent and duration of signaling activities of both Janus Kinase-Signal Transducer and Activators of Transcription (JAK-STAT) and epidermal growth factor receptor (EGFR) pathways in vivo. So far, in different insect species, a variable number of SOCS and SOCS box domain-containing proteins have been identified. These proteins are categorized into different types based on their sequence diversification, leading to an alteration in structure and regulatory function. The biological roles of the many SOCS proteins have been established as a negative or positive regulator of the signaling pathways, as mentioned earlier. Here, we discussed the existing knowledge on the SOCS proteins and their involvement in different biological functions in insects, and future perspectives to further elucidate their physiological roles.