SCG2 is a Prognostic Biomarker Associated With Immune Infiltration and Macrophage Polarization in Colorectal Cancer

Colorectal cancer (CRC) is the second most lethal malignancy around the world. Limited efficacy of immunotherapy creates an urgent need for development of novel treatment targets. Secretogranin II (SCG2) is a member of the chromogranin family of acidic secretory proteins, has a role in tumor microenvironment (TME) of lung adenocarcinoma and bladder cancer. Besides, SCG2 is a stroma-related gene in CRC, its potential function in regulating tumor immune infiltration of CRC needs to be fully elucidated. In this study, we used western blot, real-time PCR, immunofluorescence and public databases to evaluate SCG2 expression levels and distribution. Survival analysis and functional enrichment analysis were performed. We examined TME and tumor infiltrating immune cells using ESTIMATE and CIBERSORT algorithm. The results showed that SCG2 expression was significantly decreased in CRC tumor tissues, and differentially distributed between tumor and adjacent normal tissues. SCG2 was an independent prognostic predictor in CRC. High expression of SCG2 correlated with poor survival and advanced clinical stage in CRC patients. SCG2 might regulate multiple tumor- and immune-related pathways in CRC, influence tumor immunity by regulating infiltration of immune cells and macrophage polarization in CRC.

Fidelity of Cotranslational Protein Targeting to the Endoplasmic Reticulum

Fidelity of protein targeting is essential for the proper biogenesis and functioning of organelles. Unlike replication, transcription and translation processes, in which multiple mechanisms to recognize and reject noncognate substrates are established in energetic and molecular detail, the mechanisms by which cells achieve a high fidelity in protein localization remain incompletely understood. Signal recognition particle (SRP), a conserved pathway to mediate the localization of membrane and secretory proteins to the appropriate cellular membrane, provides a paradigm to understand the molecular basis of protein localization in the cell. In this chapter, we review recent progress in deciphering the molecular mechanisms and substrate selection of the mammalian SRP pathway, with an emphasis on the key role of the cotranslational chaperone NAC in preventing protein mistargeting to the ER and in ensuring the organelle specificity of protein localization.

Snake Venom Proteomics of Samar Cobra (Naja samarensis) from the Southern Philippines: Short Alpha-Neurotoxins as the Dominant Lethal Component Weakly Cross-Neutralized by the Philippine Cobra Antivenom

The Samar Cobra, Naja samarensis, is endemic to the southern Philippines and is a WHO-listed Category 1 venomous snake species of medical importance. Envenomation caused by N. samarensis results in neurotoxicity, while there is no species-specific antivenom available for its treatment. The composition and neutralization of N. samarensis venom remain largely unknown to date. This study thus aimed to investigate the venom proteome of N. samarensis for a comprehensive profiling of the venom composition, and to examine the immunorecognition as well as neutralization of its toxins by a hetero-specific antivenom. Applying C18 reverse-phase high-performance liquid chromatography (RP-HPLC) and tandem mass spectrometry (LC-MS/MS), three-finger toxins (3FTx) were shown to dominate the venom proteome by 90.48% of total venom proteins. Other proteins in the venom comprised snake venom metalloproteinases, phospholipases A2, cysteine-rich secretory proteins, venom nerve growth factors, L-amino acid oxidases and vespryn, which were present at much lower abundances. Among all, short-chain alpha-neurotoxins (SαNTX) were the most highly expressed toxin within 3FTx family, constituting 65.87% of the total venom proteins. The SαNTX is the sole neurotoxic component of the venom and has an intravenous median lethal dose (LD50) of 0.18 μg/g in mice. The high abundance and low LD50 support the potent lethal activity of N. samarensis venom. The hetero-specific antivenom, Philippine Cobra Antivenom (PCAV, raised against Naja philippinensis) were immunoreactive toward the venom and its protein fractions, including the principal SαNTX. In efficacy study, PCAV was able to cross-neutralize the lethality of SαNTX albeit the effect was weak with a low potency of 0.20 mg/ml (defined as the amount of toxin completely neutralized per milliliter of the antivenom). With a volume of 5 ml, each vial of PCAV may cross-neutralize approximately 1 mg of the toxin in vivo. The findings support the potential para-specific use of PCAV in treating envenomation caused by N. samarensis while underscoring the need to improve the potency of its neutralization activity, especially against the highly lethal alpha-neurotoxins.

Cysteine-Rich Secretory Proteins (CRISP) are Key Players in Mammalian Fertilization and Fertility

Mammalian fertilization is a complex process involving a series of successive sperm-egg interaction steps mediated by different molecules and mechanisms. Studies carried out during the past 30 years, using a group of proteins named CRISP (Cysteine-RIch Secretory Proteins), have significantly contributed to elucidating the molecular mechanisms underlying mammalian gamete interaction. The CRISP family is composed of four members (i.e., CRISP1-4) in mammals, mainly expressed in the male tract, present in spermatozoa and exhibiting Ca2+ channel regulatory abilities. Biochemical, molecular and genetic approaches show that each CRISP protein participates in more than one stage of gamete interaction (i.e., cumulus penetration, sperm-ZP binding, ZP penetration, gamete fusion) by either ligand-receptor interactions or the regulation of several capacitation-associated events (i.e., protein tyrosine phosphorylation, acrosome reaction, hyperactivation, etc.) likely through their ability to regulate different sperm ion channels. Moreover, deletion of different numbers and combination of Crisp genes leading to the generation of single, double, triple and quadruple knockout mice showed that CRISP proteins are essential for male fertility and are involved not only in gamete interaction but also in previous and subsequent steps such as sperm transport within the female tract and early embryo development. Collectively, these observations reveal that CRISP have evolved to perform redundant as well as specialized functions and are organized in functional modules within the family that work through independent pathways and contribute distinctly to fertility success. Redundancy and compensation mechanisms within protein families are particularly important for spermatozoa which are transcriptionally and translationally inactive cells carrying numerous protein families, emphasizing the importance of generating multiple knockout models to unmask the true functional relevance of family proteins. Considering the high sequence and functional homology between rodent and human CRISP proteins, these observations will contribute to a better understanding and diagnosis of human infertility as well as the development of new contraceptive options.

Cross-Kingdom Gene Coexpression Analysis Using a Stemphylium botryosum–Lens ervoides System Revealed Plasticity of Intercommunication Between the Pathogen Secretome and the Host Immune Systems

Necrotrophic pathogens are responsible for significant declines in crop yield and quality worldwide. During the infection process, a pathogen releases a series of secretory proteins to counteract the plant immune system, and this interaction of pathogen and host molecules determines whether the pathogen will successfully invade the host plant tissues. In this study, we adopted co-transcriptomic approaches to analyze the Lens ervoides–Stemphylium botryosum system, with a focus on 1,216 fungal genes coding for secretory proteins and 8,810 disease-responsive genes of the host 48, 96, and 144 h postinoculation, captured in two F9 recombinant inbred lines (RILs) displaying contrasting disease responses. By constructing in planta gene coexpression networks (GCNs) for S. botryosum, we found that the pathogen tended to co-upregulate genes regulating cell wall degradation enzymes, effectors, oxidoreductases, and peptidases to a much higher degree in the susceptible host LR-66-577 than in the resistant RIL LR-66-637, indicating that the promotion of these digestive enzymes and toxins increased S. botryosum virulence. Construction of cross-kingdom GCNs between pathogen and plant for the two RILs revealed that the co-upregulation of these fungal digestive enzymes and toxins simultaneously promoted a series of defense responses such as redox change, expression of membrane-related genes and serine/threonine kinase, and stress and disease responses in the susceptible RIL which was not observed in the resistant RIL, indicating that these activities exacerbated susceptibility to S. botryosum. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Proteomics and immunocharacterization of Asian mountain pit viper (Ovophis monticola) venom

The venomic profile of Asian mountain pit viper Ovophis monticola is clarified in the present study. Using mass spectrometry-based proteomics, 247 different proteins were identified in crude venom of O. monticola found in Thailand. The most abundant proteins were snake venom metalloproteases (SVMP) (36.8%), snake venom serine proteases (SVSP) (31.1%), and phospholipases A2 (PLA2) (12.1%). Less abundant proteins included L-amino acid oxidase (LAAO) (5.7%), venom nerve growth factor (3.6%), nucleic acid degrading enzymes (3.2%), C-type lectins (CTL) (1.6%), cysteine-rich secretory proteins (CRISP) (1.2%) and disintegrin (1.2%). The immunoreactivity of this viper’s venom to a monovalent antivenom against green pit viper Trimeresurus albolabris, or to a polyvalent antivenom against hemotoxic venom was investigated by indirect ELISA and two-dimensional (2D) immunoblotting. Polyvalent antivenom showed substantially greater reactivity levels than monovalent antivenom. A titer for the monovalent antivenom was over 1:1.28x107 dilution while that of polyvalent antivenom was 1:5.12x107. Of a total of 89 spots comprising 173 proteins, 40 spots of predominantly SVMP, SVSP and PLA2 were specific antigens for antivenoms. The 49 unrecognized spots containing 72 proteins were characterized as non-reactive proteins, and included certain types of CTLs and CRISPs. These neglected venom constituents could limit the effectiveness of antivenom-based therapy currently available for victims of pit viper envenomation.

A unified evolutionary origin for the ubiquitous protein transporters SecY and YidC

Background Protein transporters translocate hydrophilic segments of polypeptide across hydrophobic cell membranes. Two protein transporters are ubiquitous and date back to the last universal common ancestor: SecY and YidC. SecY consists of two pseudosymmetric halves, which together form a membrane-spanning protein-conducting channel. YidC is an asymmetric molecule with a protein-conducting hydrophilic groove that partially spans the membrane. Although both transporters mediate insertion of membrane proteins with short translocated domains, only SecY transports secretory proteins and membrane proteins with long translocated domains. The evolutionary origins of these ancient and essential transporters are not known. Results The features conserved by the two halves of SecY indicate that their common ancestor was an antiparallel homodimeric channel. Structural searches with SecY’s halves detect exceptional similarity with YidC homologs. The SecY halves and YidC share a fold comprising a three-helix bundle interrupted by a helical hairpin. In YidC, this hairpin is cytoplasmic and facilitates substrate delivery, whereas in SecY, it is transmembrane and forms the substrate-binding lateral gate helices. In both transporters, the three-helix bundle forms a protein-conducting hydrophilic groove delimited by a conserved hydrophobic residue. Based on these similarities, we propose that SecY originated as a YidC homolog which formed a channel by juxtaposing two hydrophilic grooves in an antiparallel homodimer. We find that archaeal YidC and its eukaryotic descendants use this same dimerisation interface to heterodimerise with a conserved partner. YidC’s sufficiency for the function of simple cells is suggested by the results of reductive evolution in mitochondria and plastids, which tend to retain SecY only if they require translocation of large hydrophilic domains. Conclusions SecY and YidC share previously unrecognised similarities in sequence, structure, mechanism, and function. Our delineation of a detailed correspondence between these two essential and ancient transporters enables a deeper mechanistic understanding of how each functions. Furthermore, key differences between them help explain how SecY performs its distinctive function in the recognition and translocation of secretory proteins. The unified theory presented here explains the evolution of these features, and thus reconstructs a key step in the origin of cells.