A highly conserved protein secreted by the prostate cancer cell line PC-3 is expressed in benign and malignant prostate tissue

The novel potential therapeutic target PSMP/MSMP promotes acute kidney injury via CCR2

Acute kidney injury (AKI) is a major worldwide health concern that currently lacks effective medical treatments. PSMP is a damage-induced chemotactic cytokine that acts as a ligand of CCR2 and has an unknown role in AKI. We have observed a significant increase in PSMP levels in the renal tissue, urine, and plasma of patients with AKI. PSMP deficiency improved kidney function and decreased tubular damage and inflammation in AKI mouse models induced by kidney ischemia-reperfusion injury, glycerol, and cisplatin. Single-cell RNA sequencing analysis revealed that Ly6Chi or F4/80lo infiltrated macrophages (IMs) were a major group of proinflammatory macrophages with strong CCR2 expression in AKI. We observed that PSMP deficiency decreased CCR2+Ly6Chi or F4/80lo IMs and inhibited M1 polarization in the AKI mouse model. Moreover, overexpressed human PSMP in the mouse kidney could reverse the attenuation of kidney injury in a CCR2-dependent manner, and this effect could be achieved without CCL2 involvement. Extracellular PSMP played a crucial role, and treatment with a PSMP-neutralizing antibody significantly reduced kidney injury in vivo. Therefore, PSMP might be a therapeutic target for AKI, and its antibody is a promising therapeutic drug for the treatment of AKI.

Antibody therapeutics for epithelial ovarian cancer

INTRODUCTION

High-grade serous ovarian carcinoma (HGSC) is an aggressive subtype of epithelial ovarian carcinoma (EOC) and remains the most lethal gynecologic cancer. A lack of effective and tolerable therapeutic options and nonspecific symptoms at presentation with advanced stage of disease are among the challenges in the management of the disease.

AREAS COVERED

An overview of ovarian cancer, followed by a discussion of the current therapeutic regimes and challenges that arise during and after the treatment of EOC. We discuss different formats of antibody therapeutics and their usage in targeting validated targets implicated in ovarian cancer, as well as three emerging novel proteins as examples recently implicated in their contribution to adaptive resistance in ovarian cancer.

EXPERT OPINION

Antibody therapeutics allow for a unique and effective way to target proteins implicated in cancer and other diseases, and have the potential to radically change the outcomes of patients suffering from ovarian cancer. The vast array of targets that have been implicated in ovarian cancer and yet the lack of effective therapeutic options for patients further stresses the importance of discovering novel proteins that can be targeted, as well as predictive biomarkers that can inform the stratification of patients into treatment-specific populations.

Functional Roles of Chemokine Receptor CCR2 and Its Ligands in Liver Disease

Chemokines are a family of cytokines that orchestrate the migration and positioning of immune cells within tissues and are critical for the function of the immune system. CCR2 participates in liver pathology, including acute liver injury, chronic hepatitis, fibrosis/cirrhosis, and tumor progression, by mediating the recruitment of immune cells to inflammation and tumor sites. Although a variety of chemokines have been well studied in various diseases, there is no comprehensive review presenting the roles of all known chemokine ligands of CCR2 (CCL2, CCL7, CCL8, CCL12, CCL13, CCL16, and PSMP) in liver disease, and this review aims to fill this gap. The introduction of each chemokine includes its discovery, its corresponding chemotactic receptors, physiological functions and roles in inflammation and tumors, and its impact on different immune cell subgroups.

Low-Input RNA-Sequencing in Patients with Cartilage Lesions, Osteoarthritis, and Healthy Cartilage

OBJECTIVE

To analyze and compare cartilage samples from 3 groups of patients utilizing low-input RNA-sequencing.

DESIGN

Cartilage biopsies were collected from patients in 3 groups (n = 48): Cartilage lesion (CL) patients had at least ICRS grade 2, osteoarthritis (OA) samples were taken from patients undergoing knee replacement, and healthy cartilage (HC) was taken from ACL-reconstruction patients without CLs. RNA was isolated using an optimized protocol. RNA samples were assessed for quality and sequenced with a low-input SmartSeq2 protocol.

RESULTS

RNA isolation yielded 48 samples with sufficient quality for sequencing. After quality control, 13 samples in the OA group, 9 in the HC group, and 9 in the CL group were included in the analysis. There was a high degree of co-clustering between the HC and CL groups with only 6 genes significantly up- or downregulated. OA and the combined HC/CL group clustered significantly separate from each other, yielding 659 significantly upregulated and 1,369 downregulated genes. GO-term analysis revealed that genes matched to cartilage and connective tissue development terms.

CONCLUSION

The gene expression profiles from the 3 groups suggest that there are no major differences in gene expression between cartilage from knees with a cartilage injury and knees without an apparent cartilage injury. OA cartilage, as expected, showed markedly different gene expression from the other 2 groups. The gene expression profiles resulting from this low-input RNA-sequencing study offer opportunities to discover new pathways not previously recognized that may be explored in future studies.

Three-dimensional structures of avian beta-microseminoproteins: insight from the chicken egg-specific beta-microseminoprotein 3 paralog

Beta‐microseminoproteins (MSMBs) are small disulfide‐rich proteins that are conserved among vertebrates. These proteins exhibit diverse biological activities and were mainly reported to play a role in male fertility, immunity, and embryogenesis. In this work, we focused on the chicken MSMB3 protein that was previously depicted as an egg antibacterial protein. We report that MSMB3 protein is exclusively expressed in the reproductive tissues of laying hens (in contrast to chicken MSMB1 and MSMB2 paralogs), to be incorporated in the egg white during the process of egg formation. We also showed that chicken MSMB3 possesses highly conserved orthologs in bird species, including Neognathae and Palaeognathae. Chicken MSMB3 was purified from egg white using heparin affinity chromatography and was analyzed by top‐down and bottom‐up proteomics. Several proteoforms could be characterized, and a homodimer was further evidenced by NMR spectroscopy. The X‐ray structure of chicken MSMB3 was solved for the first time, revealing that this protein adopts a novel dimeric arrangement. The highly cationic MSMB3 protein exhibits a distinct electrostatic distribution compared with chicken MSMB1 and MSMB2 structural models, and with published mammalian MSMB structures. The specific incorporation of MSMB3 paralog in the egg, and its phylogenetic conservation in birds together with its peculiar homodimer arrangement and physicochemical properties, suggests that the MSMB3 protein has evolved to play a critical role during the embryonic development of avian species. These new data are likely to stimulate research to elucidate the structure/function relationships of MSMB paralogs and orthologs in the animal kingdom.

PC3-Secreted Microprotein Is Expressed in Glioblastoma Stem-Like Cells and Human Glioma Tissues

Glioblastoma multiforme (GBM) is the most prevalent malignant primary brain tumor with a high recurrence rate. Despite multimodal therapy including surgical resection, chemotherapy, and radiotherapy, the median survival time after the initial diagnosis of GBM is approximately 14 months. Since cancer stem cells (CSCs) are considered the leading cause of cancer recurrence, glioblastoma stem cell-targeted therapy is a promising strategy for the treatment of GBM. However, because CSC heterogeneity has been implicated in the difficulties of CSC-target therapy, more in-depth knowledge of CSC biology is still required to develop novel therapies. In this study, we established single cell-derived tumorspheres from human glioblastoma U87MG cells. One of these tumorspheres, P4E8 clone, showed CSC-like phenotypes, such as self-renewal capacity, expression of CSC markers, resistance to anti-cancer agents, and in vivo tumorigenicity. Therefore, we used P4E8 cells as a cell-based model of glioblastoma stem cells (GSCs). Gene expression analysis using microarray indicated that the most highly expressed genes in P4E8 cells compared to the parental U87MG were PC3-secreted microprotein (MSMP). Furthermore, MSMP was expressed in patient-derived GSCs and human glioma tissues at the protein level, implying that MSMP might contribute to glioma development and progression.

PSMP/MSMP promotes hepatic fibrosis through CCR2 and represents a novel therapeutic target

BACKGROUND & AIMS

C-C motif chemokine receptor 2 (CCR2) has been recognized as a promising target for the treatment of liver fibrosis. PC3-secreted microprotein (PSMP)/microseminoprotein (MSMP) is a novel chemotactic cytokine and its receptor is CCR2. In the present study we investigated the expression and role of PSMP in liver fibrosis/cirrhosis.

METHODS

PSMP expression was studied in patients with fibrosis/cirrhosis and in 3 murine models of liver fibrosis, including mice treated with carbon tetrachloride (CCl₄), bile-duct ligation, or a 5-diethoxycarbonyl-1,4-dihydrocollidine diet. The role of PSMP was evaluated in Psmp^-/- mice and after treatment with a PSMP antibody in wild-type mice. The direct effects of PSMP on macrophages and hepatic stellate cells were studied in vitro.

RESULTS

In this study, we found that PSMP was highly expressed in fibrotic/cirrhotic tissues from patients with different etiologies of liver disease and in the 3 experimental mouse models of fibrosis. Damage-associated molecular pattern molecules HMGB-1 and IL-33 induced hepatocytes to produce PSMP. PSMP deficiency resulted in a marked amelioration of hepatic injury and fibrosis. In CCl₄-induced hepatic injury, the infiltration of macrophages and CCR2⁺ monocytes into the liver was significantly decreased in Psmp^-/- mice. Consistent with the decreased levels of intrahepatic macrophages, proinflammatory cytokines were significantly reduced. Moreover, adeno-associated virus-8 vectors successfully overexpressing human PSMP in Psmp^-/- mouse livers could reverse the attenuation of liver injury and fibrosis induced by CCl₄ in a CCR2-dependent manner. Treatment with a specific PSMP-neutralizing antibody, 3D5, prevented liver injury and fibrosis induced by CCl₄ in mice. At the cellular level, PSMP directly promoted M1 polarization of macrophages and activation of LX-2 cells.

CONCLUSION

PSMP enhances liver fibrosis through its receptor, CCR2. PSMP is a potentially attractive therapeutic target for the treatment of patients with liver fibrosis.

LAY SUMMARY

Our present study identifies the essential role of the protein PSMP for the development and progression of liver fibrosis in humans and mice. PSMP promotes liver fibrosis through inflammatory macrophage infiltration, polarization and production of proinflammatory cytokines, as well as direct activation of hepatic stellate cells via its receptor CCR2. A PSMP antibody can significantly reduce liver fibrosis development in vivo. These findings indicate that PSMP is a potential therapeutic target and its antibody is a potential therapeutic agent for the treatment of liver fibrosis.

Elevated Expression Levels of PC3-Secreted Microprotein (PSMP) in Prostate Cancer Associated With Increased Xenograft Growth and Modification of Immune-Related Microenvironment

Prostate cancer (PCa), especially metastatic PCa, is one of the main cancer types accounting for male mortality worldwide. Over decades, researchers have tried to search for effective curative methods for PCa, but many attempts have failed. The therapeutic failure of PCa is usually due to off-target or side effects; thus, finding a key molecule that could prevent PCa metastatic progression has become the most important goal for curing aggressive PCa. In this study, we collected hundreds of PCa tissues and serum and urine samples from patients to verify the upregulated expression of PC3-secreted microprotein (PSMP) in PCa tumor tissues with high Gleason scores. According to biopsy results, PSMP expression was found related to extraprostatic extension (EPE), contributing to PCa metastasis. Mechanistically, recombinant PSMP protein could promote the proliferation both in vitro and in vivo, and rhPSMP could promote epithelial–mesenchymal transition (EMT) of PC3 in vitro. Additionally, PSMP could also influence cytokine production in the xenograft model and monocyte migration and macrophage polarization in vitro. Our most important finding was that neutralizing antibodies against PSMP could suppress xenograft PC3 growth and promote the survival of PC3 metastatic mice model, providing an effective option to cure human PCa.

Induction of anti-VEGF therapy resistance by upregulated expression of microseminoprotein (MSMP)

Anti-vascular endothelial growth factor (VEGF) therapy has demonstrated efficacy in treating human metastatic cancers, but therapeutic resistance is a practical limitation and most tumors eventually become unresponsive. To identify microenvironmental factors underlying the resistance of cancer to antiangiogenesis therapy, we conducted genomic analyses of intraperitoneal ovarian tumors in which adaptive resistance to anti-VEGF therapy (B20 antibody) developed. We found that expression of the microseminoprotein, prostate-associated (MSMP) gene was substantially upregulated in resistant compared with control tumors. MSMP secretion from cancer cells was induced by hypoxia, triggering MAPK signaling in endothelial cells to promote tube formation in vitro. Recruitment of the transcriptional repressor CCCTC-binding factor (CTCF) to the MSMP enhancer region was decreased by histone acetylation under hypoxic conditions in cancer cells. MSMP siRNA, delivered in vivo using the DOPC nanoliposomes, restored tumor sensitivity to anti-VEGF therapy. In ovarian cancer patients treated with bevacizumab, serum MSMP concentration increased significantly only in non-responders. These findings imply that MSMP inhibition combined with the use of antiangiogenesis drugs may be a new strategy to overcome resistance to antiangiogenesis therapy.

The PSMP-CCR2 interactions trigger monocyte/macrophage-dependent colitis

Monocytes/macrophages have been found to be an important component of colitis. However, the key chemokine that initiates the CCR2⁺ monocytes migration from circulation to colitis tissue remains to be undiscovered. PC3-secreted microprotein (PSMP) is a novel chemokine whose receptor is CCR2. The physiological and pathological functions of PSMP have not yet been reported. In this study, PSMP was found to be expressed in colitis and colonic tumor tissues from patients and significantly up-regulated in mouse DSS-induced colitis tissues. PSMP overexpression in the colon aggravated the DSS-induced colitis and the anti-PSMP neutralizing antibody mollified the colitis by reducing macrophage infiltration and inhibiting the expression of IL-6, TNF-α and CCL2. Furthermore, we demonstrated that lipopolysaccharide and muramyl dipeptide induced PSMP expression in the colonic epithelial cells. PSMP was up-regulated in the initial stage prior to IL-6, TNF-α and CCL2 up-regulated expression in DSS colitis and promoted the M1 macrophages to produce CCL2. PSMP chemo-attracted Ly6C^hi monocytes in a CCR2 dependent manner via in situ chemotaxis and adoptive transfer assays. Our data identify PSMP as a key molecule in ulcerative colitis, which provides a novel mechanism of monocyte/macrophage migration that affects gut innate immunity and makes PSMP a potential target for controlling colitis.

Isotope-targeted glycoproteomics (IsoTaG): a mass-independent platform for intact N- and O-glycopeptide discovery and analysis

Protein glycosylation is a heterogeneous post-translational modification (PTM) that plays an essential role in biological regulation. However, the diversity found in glycoproteins has undermined efforts to describe the intact glycoproteome via mass spectrometry (MS). We present IsoTaG, a mass-independent chemical glycoproteomics platform for characterization of intact, metabolically labeled glycopeptides at the whole-proteome scale. In IsoTaG, metabolic labeling of the glycoproteome is combined with (i) chemical enrichment and isotopic recoding of glycopeptides to select peptides for targeted glycoproteomics using directed MS and (ii) mass-independent assignment of intact glycopeptides. We structurally assigned 32 N-glycopeptides and over 500 intact and fully elaborated O-glycopeptides from 250 proteins across three human cancer cell lines and also discovered unexpected peptide sequence polymorphisms (pSPs). The IsoTaG platform is broadly applicable to the discovery of PTM sites that are amenable to chemical labeling, as well as previously unknown protein isoforms including pSPs.

PC3-secreted microprotein is a novel chemoattractant protein and functions as a high-affinity ligand for CC chemokine receptor 2

PC3-secreted microprotein (PSMP) or microseminoprotein is a newly discovered secreted protein whose function is currently unknown. In this study, PSMP was found to possess chemotactic ability toward monocytes and lymphocytes, and its functional receptor was identified as CCR2B. PSMP was identified as a chemoattractant protein from a PBMC chemoattractant platform screen that we established. The mature secreted PSMP was able to chemoattract human peripheral blood monocytes, PBLs, and CCR2B-expressing THP-1 cells, but not peripheral blood neutrophils, even though it does not contain the classical structure of chemokines. CCR2B was identified as one receptor for PSMP-mediated chemotaxis by screening HEK293 cells that transiently expressed classical chemokine receptors; results obtained from the chemotaxis, calcium flux, receptor internalization, and radioligand-binding assays all confirmed this finding. To further identify the major function of PSMP, we analyzed its expression profile in tissues. PSMP is highly expressed in benign prostatic hyperplasia and in some prostate cancers, and can also be detected in breast tumor tissue. In response to PSMP stimulation, phosphorylated ERK levels downstream of CCR2B signaling were upregulated in the PC3 cell line. Taken together, our data collectively suggest that PSMP is a chemoattractant protein acting as a novel CCR2 ligand that may influence inflammation and cancer development.

A novel MSMB-related microprotein in the postovulatory egg coats of marsupials

BACKGROUND

Early marsupial conceptuses differ markedly from those of eutherian mammals, especially during cleavage and early blastocyst stages of development. Additionally, in marsupials the zona pellucida is surrounded by two acellular layers, the mucoid coat and shell, which are formed from secretions from the reproductive tract.

RESULTS

We report the identification of a novel postovulatory coat component in marsupials, which we call uterinesecreted microprotein (USM). USM belongs to a family of disulfide-rich microproteins of unconfirmed function that is found throughout deuterostomes and in some protostomes, and includes β-microseminoprotein (MSMB) and prostate-associated microseminoprotein (MSMP). We describe the evolution of this family in detail, including USM-related sequences in other vertebrates. The orthologue of USM in the tammar wallaby, USM1, is expressed by the endometrium with a dynamic temporal profile, possibly under the control of progesterone.

CONCLUSIONS

USM appears to have evolved in a mammalian ancestor specifically as a component of the postovulatory coats. By analogy with the known properties of MSMB, it may have roles in regulating sperm motility/survival or in the immune system. However, its C-terminal domain is greatly truncated compared with MSMB, suggesting a divergent function.

Rapidly evolving marmoset MSMB genes are differently expressed in the male genital tract

BACKGROUND

Beta-microseminoprotein, an abundant component in prostatic fluid, is encoded by the potential tumor suppressor gene MSMB. Some New World monkeys carry several copies of this gene, in contrast to most mammals, including humans, which have one only. Here we have investigated the background for the species difference by analyzing the chromosomal organization and expression of MSMB in the common marmoset (Callithrix jacchus).

METHODS

Genes were identified in the Callithrix jacchus genome database using bioinformatics and transcripts were analyzed by RT-PCR and quantified by real time PCR in the presence of SYBR green.

RESULTS

The common marmoset has five MSMB: one processed pseudogene and four functional genes. The latter encompass homologous genomic regions of 32-35 kb, containing the genes of 12-14 kb and conserved upstream and downstream regions of 14-19 kb and 3-4 kb. One gene, MSMB1, occupies the same position on the chromosome as the single human gene. On the same chromosome, but several Mb away, is another MSMB locus situated with MSMB2, MSMB3 and MSMB4 arranged in tandem. Measurements of transcripts demonstrated that all functional genes are expressed in the male genital tract, generating very high transcript levels in the prostate. The transcript levels in seminal vesicles and testis are two and four orders of magnitude lower. A single gene, MSMB3, accounts for more than 90% of MSMB transcripts in both the prostate and the seminal vesicles, whereas in the testis around half of the transcripts originate from MSMB2. These genes display rapid evolution with a skewed distribution of mutated nucleotides; in MSMB2 they affect nucleotides encoding the N-terminal Greek key domain, whereas in MSMB3 it is the C-terminal MSMB-unique domain that is affected.

CONCLUSION

Callitrichide monkeys have four functional MSMB that are all expressed in the male genital tract, but the product from one gene, MSMB3, will predominate in seminal plasma. This gene and MSMB2, the predominating testicular gene, have accumulated mutations that affect different parts of the translation products, suggesting an ongoing molecular specialization that presumably yields functional differences in accessory sex glands and testis.

The cotton-top tamarin (Saguinus oedipus) has five beta-microseminoprotein genes, two of which are pseudogenes

beta-Microseminoprotein (MSP) is one of the most abundant proteins in human seminal plasma and is secreted from the prostate gland. Its evolution can be traced from primates down to nonvertebrate species such as amphioxus, despite substantial differences in the primary structure. Most mammals are known to have one single MSP gene, but we have previously shown that the cotton-top tamarin and the common marmoset-two New World monkeys-carry several MSP genes. In this study we continue our characterization of MSP genes in the cotton-top tamarin by presenting the full nucleotide sequence of the three previously identified genes, mspA, mspE, and mspJ. A promoter analysis using the luciferase reporter showed that mspE is as transcriptionally active as the single human MSP gene, whereas mspA and mspJ display no activity with this assay. Two novel MSP genes were also identified, mspB and mspH, both of which are pseudogenes. MspB has a frameshift mutation in the third exon resulting in a new C-terminus and premature stop of translation. MspH has the features of a processed pseudogene, originating from a transcript of mspE. It is integrated into the genome together with another processed pseudogene originating from a transcript of the nucleoporin gene NUP88. The MSP genes described in this study probably arose by phylogenetically rather late duplication or retrotransposition, suggesting that they are confined to a limited number of New World monkeys.