MDA-9/syntenin is essential for factor VIIa-induced signaling, migration, and metastasis in melanoma cells

The Multifunctional Protein Syntenin-1: Regulator of Exosome Biogenesis, Cellular Function, and Tumor Progression

Syntenin acts as an adaptor and scaffold protein through its two PSD-95, Dlg, and ZO-1 (PDZ) domains, participating in multiple signaling pathways and modulating cellular physiology. It has been identified as an oncogene, promoting cancer development, metastasis, and angiogenesis in various carcinomas. Syntenin-1 is also associated with the production and release of exosomes, small extracellular vesicles that play a significant role in intercellular communication by containing bioactive molecules such as proteins, lipids, and nucleic acids. The trafficking of exosomes involves a complex interplay of various regulatory proteins, including syntenin-1, which interacts with its binding partners, syndecan and activated leukocyte cell adhesion molecule (ALIX). Exosomal transfer of microRNAs, a key cargo, can regulate the expression of various cancer-related genes, including syntenin-1. Targeting the mechanism involving the regulation of exosomes by syntenin-1 and microRNAs may provide a novel treatment strategy for cancer. This review highlights the current understanding of syntenin-1's role in regulating exosome trafficking and its associated cellular signaling pathways.

Global downregulation of pigmentation-associated genes in human premature hair graying

Premature hair graying, or canities, is a complex multi-factorial process with negative effects on affected individuals. The aim of the present study was to investigate the possible underlying mechanisms of premature hair graying at the genetic level. A total of 5 unrelated Han Chinese individuals presenting with premature hair graying (25–40 years old, with >1% hair affected) were enrolled in the present study. RNA sequencing was performed to identify gene expression changes between the follicular cells of grey and black hair from the cohort. A total of 127 differentially expressed genes (DEGs) were identified. These DEGs were overrepresented in categories associated with the pigmentation pathway, with a decreased expression of key genes responsible for melanin synthesis. Of note, the decreased expression of certain transcription factors and the increased expression of certain precursor microRNAs observed may explain for the downregulation of certain other DEGs, which were identified as their targets via Starbase v2 and Integrated Motif Activity Response Analysis. The DEGs were also enriched in terms associated with the nervous system, indicating that neural disturbances may also have certain roles in premature hair graying. Of note, five of the downregulated DEGs were associated with aging according to the JenAge Aging Factor Database. To the best of our knowledge, the present study was the first genome-wide survey of the gene expression profile associated with premature hair graying. Dysfunction of the melanin biosynthesis pathway is probably the direct cause of hair graying and the present results provide valuable clues for further functional and mechanistic investigation.

A PDZ Protein MDA-9/Syntenin: As a Target for Cancer Therapy

Melanoma differentiation-associated gene 9 (MDA-9)/Syntenin is a multidomain PDZ protein and identified as a key oncogene in melanoma initially. This protein contains a unique tandem PDZ domain architecture (PDZ1 and PDZ2 spaced by a 4-amino acid linker), an N-terminal domain (NTD) that is structurally uncharacterized and a short C-terminal domain (CTD). The PDZ1 domain is regarded as the PDZ signaling domain while PDZ2 served as the PDZ superfamily domain. It has various cellular roles by regulating many of major signaling pathways in numerous cancertypes. Through the use of novel drug design methods, such as dimerization and unnatural amino acid substitution of inhibitors in our group, the protein may provide a valuable therapeutic target. The objective of this review is to provide a current perspective on the cancer-specific role of MDA-9/Syntenin in order to explore its potential for cancer drug discovery and cancer therapy.

Dasatinib inhibits c-src phosphorylation and prevents the proliferation of Triple-Negative Breast Cancer (TNBC) cells which overexpress Syndecan-Binding Protein (SDCBP)

Triple negative breast cancer (TNBC) progresses rapidly but lacks effective targeted therapies. Our previous study showed that downregulating syndecan-binding protein (SDCBP) in TNBC inhibits the proliferation of TNBC cells. Dasatinib is a new small-molecule inhibitor of c-src phosphorylation. The aim of this study was to investigate if SDCBP is a potential marker to indicate whether a TNBC is suitable for dasatinib therapy. This study applied co-immunoprecipitation to identify the interaction between SDCBP and c-src in TNBC cell lines. In addition, immunohistochemistry was used to investigate SDCBP and tyrosine-419 phosphorylated c-src (p-c-src-Y419) expression in TNBC tissues. SDCBP-overexpressing MDA-MB-231 cells were then constructed to evaluate the effects of dasatinib on SDCBP-induced TNBC progression in vitro and tumor formation in nude mice. We found wild-type SDCBP interacted with c-src and promoted the phosphorylation of c-src; this phosphorylation was completely blocked by dasatinib. SDCBP lacking the PDZ domain had no such effect. Among the 52 consecutive random TNBC cases examined, the expression of SDCBP was consistent with that of p-c-src-Y419, and positively correlated with histological grading or Ki-67 levels. SDCBP overexpression significantly accelerated the proliferation and cell cycle progression of the TNBC cell line MDA-MB-231; these effects were prevented by dasatinib treatment. However, the subsequent inhibition of p27 expression partially restored the proliferation and viability of the TNBC cells. The results of this study suggest that SDCBP interacts with c-src, regulates G1/S in TNBC cells, and enhances tumor cell proliferation by promoting the tyrosine phosphorylation of c-src at residue 419. Dasatinib inhibits such phosphorylation and blocks SDCBP-induced cell cycle progression. Therefore, SDCBP might be an important marker for identifying TNBC cases that are suitable for dasatinib therapy.

MDA-9/Syntenin Control

MDA-9/Syntenin is a small PDZ domain containing scaffolding protein with diverse array of functions regulating membrane trafficking, cell adhesion, neural, and synaptic development, ubiquitination, and exosome biogenesis. An appreciable number of studies also established a pivotal role of MDA-9/Syntenin in cancer development and progression. In this review, we will discuss the dynamic role of MDA-9/Syntenin in regulating normal and abnormal fate of various cellular processes.