TAIL1: an isthmin-like gene, containing type 1 thrombospondin-repeat and AMOP domain, mapped to ARVD1 critical region

Isthmin: A multifunctional secretion protein

Isthmin is a polypeptide secreted by adipocytes that was first detected in Xenopus gastrula embryos. Recent studies have focused on the biological functions of isthmin in growth and development, angiogenesis, and metabolism. Distinct spatiotemporal expression of isthmin-1 (ISM-1) was observed during growth and development. ISM-1 plays an important role in the occurrence and development of cancer by regulating cell proliferation, migration, angiogenesis, and immune microenvironments. Moreover, ISM-1, as a newly identified insulin-like adipokine, increases adipocyte glucose uptake and inhibits hepatic lipid synthesis. However, the biological function of ISM-1 remains largely unknown. In this review, we highlight the structure and physiological functions of isthmin and explore its application potential, contributing to a better understanding of its function and providing prevention and treatment strategies for various diseases.

Advances in research of biological functions of Isthmin-1

Isthmin-1 (ISM1) was initially thought to be a brain secretory factor, but with the development of technical means of research and the refinement of animal models, numerous studies have shown that this molecule is expressed in multiple tissues, suggesting that it may have multiple biological functions. As a factor that regulates growth and development, ISM1 is expressed in different animals with spatial and temporal variability and can coordinate the normal development of multiple organs. Recent studies have found that under the dependence of a non-insulin pathway, ISM1 can lower blood glucose, inhibit insulin-regulated lipid synthesis, promote protein synthesis, and affect the body's glucolipid and protein metabolism. In addition, ISM1 plays an important role in cancer development by promoting apoptosis and anti-angiogenesis, and by regulating multiple inflammatory pathways to influence the body's immune response. The purpose of this paper is to summarize relevant research results from recent years and to describe the key features of the biological functions of ISM1. We aimed to provide a theoretical basis for the study of ISM1 related diseases, and potential therapeutic strategies. The main biological functions of ISM1. Current studies on the biological functions of ISM1 focus on growth and development, metabolism, and anticancer treatment. During embryonic development, ISM1 is dynamically expressed in the zebrafish, African clawed frog, chick, mouse, and human, is associated with craniofacial malformations, abnormal heart localization, and hematopoietic dysfunction. ISM1 plays an important role in regulating glucose metabolism, lipid metabolism, and protein metabolism in the body. ISM1 affects cancer development by regulating cellular autophagy, angiogenesis, and the immune microenvironment.

A brief overview about the adipokine: Isthmin-1

Isthmin-1 is a secreted protein with multiple capability; however, it truly attracts our attention since the definition as an adipokine in 2021, which exerts indispensable roles in various pathophysiological processes through the endocrine or autocrine manners. In this review, we summarize recent knowledge of isthmin-1, including its distribution, structure, receptor and potential function.

Zebrafish Ism1 is a novel antiviral factor that positively regulates antiviral immune responses

Isthmin1 (Ism1), first identified as a secreted protein in Xenopus embryos in 2002, has been shown to perform multiple biological functions, but little is known currently regarding its role in immunity. Here we show that the expression of ism1 is inducible by challenge with Grass carp reovirus (GCRV) in zebrafish, suggesting involvement of Ism1 in antiviral response. We then demonstrate that recombinant Ism1 (rIsm1) reduces the cytopathic effect in the cells infected by GCRV, promotes the expression of type I IFN gene and IFN-inducible antiviral protein Mxa gene, and reduces the virus quantity in virus-infected cells and host. We also show that rIsm1 promotes the expression of tbk1, irf3 and irf7, suggesting it promotes the expression of type I IFN gene and Mxa gene via induction of Tbk1-Irf3-Ifn pathway. These data together indicate that Ism1 is a new immune-relevant factor functioning in antiviral immune response, and provides a target for controlling viral infection.

Isthmin 2 is decreased in preeclampsia and highly expressed in choriocarcinoma

Introduction

Isthmin 2 (ISM2) is a protein which expression in humans is almost specific to the placenta. There is no previous report in the literature that investigated this protein in preeclampsia or choriocarcinoma.

Methods

We conducted a prospective, cross-sectional study that included women with preeclampsia, gestational hypertension and normotensive pregnancy. We measured serum concentrations of ISM2 protein and performed immunohistochemistry in placenta tissues. We also performed immunohistochemistry of ISM2 in samples from choriocarcinoma and compare with lung, prostate, colon, gastric and breast cancers.

Results

A total of 81 patients were included, 30 with preeclampsia, 21 with gestational hypertension and 30 controls. The ISM2 protein was found to be decreased in patients with preeclampsia compared to the control group (P = 0.036). These results were confirmed by immunohistochemistry. We also found that ISM2 protein was overexpressed in choriocarcinoma.

Discussion

Taken together, our results suggest an angiogenic function for ISM2. Its serum level decreased in our patients with preeclampsia could be reflecting that it is involved in the pathogenesis of the disease; on the other hand its high expression in choriocarcinoma, indicates that ISM2 may play an active role in the angiogenesis of this and other cancers.

The role of the AMOP domain in MUC4/Y-promoted tumour angiogenesis and metastasis in pancreatic cancer

BACKGROUND

MUC4 is a high molecular weight membrane protein that is overexpressed in pancreatic cancer (PC) and is associated with the development and progression of this disease. However, the exact mechanisms through which MUC4 domains promote these biological processes have rarely been studied, partly because of its high molecular weight, difficulty to overexpress it. Here, we use MUC4/Y, one of the MUC4 transcript variants, as a model molecule to investigate the AMOP-domain of MUC4(MUC/Y).

METHODS

We used cell proliferation, migration, invasion and tube formation assays in vitro to explore the abilities of AMOP domain in PC. In vivo, the matrigel plug assay, orthotopic implantation and Kaplan-Meier survival curves were used to check the results we observed in vitro. Finally, we discovered the underlying mechanism through western blot and immunofluorescence.

RESULTS

We found that MUC4/Y overexpression could enhance the angiogenic and metastatic properties of PC cells, both in vitro and in vivo. However, the deletion of AMOP domain could cutback these phenomena. Additionally, Kaplan-Meier survival curves showed that mice injected with MUC4/Y overexpressed cells had shorter survival time, compared with empty-vector-transfected cells (MUC4/Y-EV), or cells expressing MUC4/Y without the AMOP domain (MUC4/Y-AMOP(△)). Our data also showed that overexpression of MUC4/Y could activate NOTCH3 signaling, increasing the expression of downstream genes: VEGF-A, MMP-9 and ANG-2.

CONCLUSIONS

The AMOP domain had an important role in MUC4/Y (MUC4)-mediated tumour angiogenesis and metastasis of PC cells; and the NOTCH3 signaling was involved. These findings provided new insights into PC therapies. Our study also supplies a new method to study other high molecular membrane proteins.

Isthmin 1 is a secreted protein expressed in skin, mucosal tissues, and NK, NKT, and th17 cells

Using a comprehensive microarray database of human gene expression, we identified that in mammals, a secreted protein known as isthmin 1 (ISM1) is expressed in skin, mucosal tissues, and selected lymphocyte populations. ISM1 was originally identified in Xenopus brain during development, and it encodes a predicted ∼50-kDa protein containing a signal peptide, a thrombospondin domain, and an adhesion-associated domain. We confirmed the pattern of expression of ISM1 in both human and mouse tissues. ISM1 is expressed by DX5(+) lung lymphocytes that include NK and NKT-like cells, and is also expressed by some CD4(+) T cells upon activation but its expression increases significantly when CD4(+) T cells were polarized to the Th17 lineage in vitro. The presence of IFN-γ during CD4(+) T cell polarization inhibits ISM1 expression. Given that ISM1 has been reported to have anti-angiogenic properties, these observations suggest that ISM1 is a mediator of lymphocyte effector functions and may participate in both innate and acquired immune responses.

Distinct spatiotemporal expression of ISM1 during mouse and chick development

Isthmin 1 (ISM1) constitutes the founder of a new family of secreted proteins characterized by the presence of 2 functional domains: thrombospondin type 1 repeat (TSR1) and adhesion-associated domain in MUC4 and other proteins (AMOP). ISM1 was identified in the frog embryo as a member of the FGF8 synexpression group due to its expression in the brain midbrain-hindbrain boundary (MHB) or isthmus. In zebrafish, ISM1 was described as a WNT- and NODAL-regulated gene. The function of ISM1 remains largely elusive. So far, ISM1 has been described as an angiogenesis inhibitor that has a dual function in endothelial cell survival and cell death. For a better understanding of ISM1 function, we examined its spatiotemporal distribution in mouse and chick using RT-PCR, ISH, and IHC analyses. In the mouse, ISM1 transcripts are found in tissues such as the anterior mesendoderm, paraxial and lateral plate mesoderm, MHB and trunk neural tube, as well as in the somites and dermomyotome. In the newborn and adult, ISM1 is prominently expressed in the lung and brain. In addition to its putative role during embryonic and postnatal development, ISM1 may also be important for organ homeostasis in the adult. In the chick embryo, ISM1 transcripts are strongly detected in the ear, eye, and spinal cord primordia. Remarkable differences in ISM1 spatiotemporal expression were found during mouse and chick development, despite the high homology of ISM1 orthologs in these species.

Quantitative proteomic analysis of differentially expressed proteins in pancreatic cancer stem cells

AIM: To screen and identify differentially expressed proteins in pancreatic cancer stem cells.

METHODS: MIA-PaCa2 (TIC^high) and BxPc-3 (TIC^low) were used in the study. Differentially expressed proteins between MIA-PaCa2 (TIC^high) and BxPc-3 (TI^Clow) cells were isolated and screened by 2D-DIGE analysis. Protein identification was performed by peptide mass fingerprinting with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF). Western blot was performed to verify the differential expression of TRIM28.

RESULTS: Fluorescent differential protein expression patterns were obtained between MIA-PaCa2 (TIC^high) and BxPc-3 (TIC^low) cells. Analyses with DeCyder v6.5 software showed a total of 23 differentially expressed protein spots (>1.5 folds), and these protein spots were identified by mass spectrometry as 19 proteins, which are involved in cell communication and signal transduction, immune response, transcription and cell cycle regulation, adipocyte differentiation and lipid droplet formation, cytoskeletal formation, cell adhesion, transport, and translation. Western blot analysis revealed that TRIM28 was highly expressed in MIA-PaCa2 (TIC^high) cells but not expressed in BxPc-3 (TIC^low) cells. Among the 19 identified proteins, 8 were up-regulated and 11 down-regulated in MIA-PaCa2 (TIC^high) cells.

CONCLUSION: The identified differentially expressed proteins, such as TRIM28, are associated with the genesis, development and regulation of pancreatic cancer stem cells. They may become new therapeutic targets for pancreatic cancer.

Isthmin inhibits glioma growth through antiangiogenesis in vivo

Among glioma treatment strategies, antiangiogenesis emerges as a meaningful and feasible treatment approach for inducing long-term survival. Isthmin is a gene highly expressed in the isthmus of the midbrain-hindbrain organizer in Xenopus, and has recently been identified as a novel angiogenesis inhibitor. However, the potential of isthmin on the glioma angiogenesis has not been well studied. In the present study, we demonstrated that the recombinant adenovirus isthmin (Ad-isthmin) could inhibit VEGF-stimulated endothelial cell proliferation and induce apoptosis through a caspase-dependent pathway. In addition, Ad-isthmin significantly suppressed glioma growth through antiangiogenesis without apparent side effects. Taken together, our results demonstrated that isthmin could act as a novel angiogenesis inhibitor and might be utilized in the glioma antiangiogenesis therapy.

Genetics coupled to quantitative intact proteomics links heritable aphid and endosymbiont protein expression to circulative polerovirus transmission

Yellow dwarf viruses in the family Luteoviridae, which are the causal agents of yellow dwarf disease in cereal crops, are each transmitted most efficiently by different species of aphids in a circulative manner that requires the virus to interact with a multitude of aphid proteins. Aphid proteins differentially expressed in F2 Schizaphis graminum genotypes segregating for the ability to transmit Cereal yellow dwarf virus-RPV (CYDV-RPV) were identified using two-dimensional difference gel electrophoresis (DIGE) coupled to either matrix-assisted laser desorption ionization-tandem mass spectrometry or online nanoscale liquid chromatography coupled to electrospray tandem mass spectrometry. A total of 50 protein spots, containing aphid proteins and proteins from the aphid's obligate and maternally inherited bacterial endosymbiont, Buchnera, were identified as differentially expressed between transmission-competent and refractive aphids. Surprisingly, in virus transmission-competent F2 genotypes, the isoelectric points of the Buchnera proteins did not match those in the maternal Buchnera proteome as expected, but instead they aligned with the Buchnera proteome of the transmission-competent paternal parent. Among the aphid proteins identified, many were involved in energy metabolism, membrane trafficking, lipid signaling, and the cytoskeleton. At least eight aphid proteins were expressed as heritable, isoelectric point isoform pairs, one derived from each parental lineage. In the F2 genotypes, the expression of aphid protein isoforms derived from the competent parental lineage aligned with the virus transmission phenotype with high precision. Thus, these isoforms are candidate biomarkers for CYDV-RPV transmission in S. graminum. Our combined genetic and DIGE approach also made it possible to predict where several of the proteins may be expressed in refractive aphids with different barriers to transmission. Twelve proteins were predicted to act in the hindgut of the aphid, while six proteins were predicted to be associated with the accessory salivary glands or hemolymph. Knowledge of the proteins that regulate virus transmission and their predicted locations will aid in understanding the biochemical mechanisms regulating circulative virus transmission in aphids, as well as in identifying new targets to block transmission.

Genetic bases of arrhythmogenic right ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disease in which the pathological substrate is a fibro-fatty replacement of the right ventricular myocardium. The major clinical features are different types of arrhythmias with a left branch block pattern. ARVC shows autosomal dominant inheritance with incomplete penetrance. Recessive forms were also described, although in association with skin disorders.

Ten genetic loci have been discovered so far and mutations were reported in five different genes. ARVD1 was associated with regulatory mutations of transforming growth factor beta-3 (TGFβ3), whereas ARVD2, characterized by effort-induced polymorphic arrhythmias, was associated with mutations in cardiac ryanodine receptor-2 (RYR2). All other mutations identified to date have been detected in genes encoding desmosomal proteins: plakoglobin (JUP) which causes Naxos disease (a recessive form of ARVC associated with palmoplantar keratosis and woolly hair); desmoplakin (DSP) which causes the autosomal dominant ARVD8 and plakophilin-2 (PKP2) involved in ARVD9. Desmosomes are important cell-to-cell adhesion junctions predominantly found in epidermis and heart; they are believed to couple cytoskeletal elements to plasma membrane in cell-to-cell or cell-to-substrate adhesions.