Project description:The fetal isoform A of the insulin receptor (IR-A) is frequently overexpressed in a variety of malignancies including breast cancer. IR overexpression has a recognized role in cancer progression and resistance to anticancer therapies. In particular, IR-A has a peculiar mitogenic potential and is activated not only by insulin but also by IGF-2. Previously, we identified discoidin domain receptor 1 (DDR1) as a new IR-A interacting protein. DDR1, a non-integrin collagen tyrosine kinase receptor, is overexpressed in several malignancies and plays a role in cancer progression and metastasis.We now evaluated whether DDR1 is able to exert a role in breast cancer biology by functionally cross-talking with IR. In MCF-7 human breast cancer cells, IR and DDR1 co-immunoprecipitated and co-localized after insulin or IGF-2 stimulation. In a panel of breast cancer cells, DDR1 knockdown by specific siRNAs markedly inhibited IR downstream signaling as well as proliferation, migration and colony formation in response to insulin and IGF-2. These effects were accompanied by reduction of IR protein and mRNA expression, which involved both transcriptional and post-transcriptional effects. DDR1 overexpression elicited opposite effects. Bioinformatics analysis of public domain databases showed that IR and DDR1 co-expression significantly correlates with several clinically relevant histopathological and molecular features of human breast carcinomas.These findings demonstrate that, in human breast cancer cells, DDR1 regulates IR expression and ligand dependent biological actions. This novel functional crosstalk is likely clinically relevant and may become a new molecular target in breast cancer.
Project description:ObjectiveTo evaluate the association between promoter DNA methylation and discoidin domain receptor 1 (DDR1) gene expression in men with nonobstructive azoospermia (NOA).DesignComparing fibroblasts cultured from testicular biopsies using a high resolution Infinium 450K methylation array.SettingBasic research laboratory.Patient(s)Men with NOA (n = 16) and with normal spermatogenesis (n = 5).Intervention(s)None.Main outcome measure(s)Bisulfite clonal sequencing for validation and quantification of CpG methylation of DDR1; gene expression analysis of DDR1 with quantitative polymerase chain reaction and immunohistochemistry to validate the array results at mRNA and protein levels.Result(s)We validated promoter methylation, mRNA and protein levels of the CpG sites identified from array results. Differentially methylated CpG sites (∼20K) were identified using an F-test in the NOA samples. We identified 20 genes with >30% difference in DNA methylation within the promoter region of men with NOA and fertile controls. Of the aberrantly methylated genes, 10 were hypomethylated and 10 were hypermethylated genes. From the top 10 hypermethylated genes, six genes (MRI1, DCAF12L1, TMEM95, CECR2, DDR1, and NPHS2) were selected for validation because they were shown to be expressed in the testis. Of the six genes expressed in the fibroblasts cultured from testis, DDR1 showed an abnormal gene expression pattern. Three patients (19%) out of the 16 men with NOA for whom gene expression data were available had lower DDR1 expression levels (1.8x fold decrease) than the fertile men, whereas four (25%) men had higher expression levels (2x fold increase) of DDR1 compared with the levels in fertile men. Quantitative analysis by bisulfite clonal sequencing showed that one of the CpG sites (cg13329862) of DDR1 promoter was hypermethylated in NOA patients compared with fertile controls (53% vs. 15%). Immunohistochemical analysis suggests presence of DDR1 within cytoplasm of germ cells and peritubular connective tissue (in men with hypospermatogenesis) and decreased expression of the protein in men with Sertoli-cell only syndrome.Conclusion(s)Abnormal gene expression of DDR1 is associated with NOA. The functional relevance of aberrant methylation of DDR1 to expression of DDR1 in men with NOA warrants further investigation.
Project description:The evolutionarily conserved serine-threonine kinase mammalian target of rapamycin (mTOR) plays a critical role in regulating many pathophysiological processes. Functional characterization of the mTOR signaling pathways, however, has been hampered by the paucity of known substrates. We used large-scale quantitative phosphoproteomics experiments to define the signaling networks downstream of mTORC1 and mTORC2. Characterization of one mTORC1 substrate, the growth factor receptor-bound protein 10 (Grb10), showed that mTORC1-mediated phosphorylation stabilized Grb10, leading to feedback inhibition of the phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated, mitogen-activated protein kinase (ERK-MAPK) pathways. Grb10 expression is frequently down-regulated in various cancers, and loss of Grb10 and loss of the well-established tumor suppressor phosphatase PTEN appear to be mutually exclusive events, suggesting that Grb10 might be a tumor suppressor regulated by mTORC1.
Project description:Skeletal muscle of livestock is composed of both fast- and slow-twitch muscle fibers, which are key factors in their meat quality. However, the role of protein phosphorylation in muscle fiber type is not completely understood. Here, a fast-twitch (biceps femoris, BF) and slow-twitch (soleus, SOL) muscle tissue sample was collected from three male offspring of Duroc and Meishan pigs. We demonstrate that the meat quality of SOL muscle is significantly better than that of BF muscle. We further used phosphoproteomic profiling of BF and SOL muscles to identify differences between these muscle types. A total of 2,327 phosphorylation sites from 770 phosphoproteins were identified. Among these sites, 287 differentially expressed phosphorylation sites (DEPSs) were identified between BF and SOL. GO and KEGG enrichment analysis of proteins containing DEPSs showed that these phosphorylated proteins were enriched in the glycolytic process GO term and the AMPK signaling pathway. A protein-protein interaction (PPI) analysis reveals that these phosphorylated proteins interact with each other to regulate the transformation of muscle fiber type. These analyses reveal that protein phosphorylation modifications are involved in porcine skeletal muscle fiber type transformation. This study provides new insights into the molecular mechanisms by which protein phosphorylation regulates muscle fiber type transformation and meat quality in pigs.
Project description:Discoidin domain receptor 1 (Drd1) is a collagen-binding membrane protein, but its role in osteoblasts during osteogenesis remains undefined. We generated inducible osteoblast-specific Ddr1 knockout (OKOΔDdr1) mice; their stature at birth, body weight and body length were significantly decreased compared with those of control Ddr1f/f-4OHT mice. We hypothesize that Ddr1 regulates osteogenesis of osteoblasts. Micro-CT showed that compared to 4-week-old Ddr1f/f-4OHT mice, OKOΔDdr1 mice presented significant decreases in cancellous bone volume and trabecular number and significant increases in trabecular separation. The cortical bone volume was decreased in OKOΔDdr1 mice, resulting in decreased mechanical properties of femurs compared with those of Ddr1f/f-4OHT mice. In femurs of 4-week-old OKOΔDdr1 mice, H&E staining showed fewer osteocytes and decreased cortical bone thickness than Ddr1f/f-4OHT. Osteoblast differentiation markers, including BMP2, Runx2, alkaline phosphatase (ALP), Col-I and OC, were decreased compared with those of control mice. Ddr1 knockdown in osteoblasts resulted in decreased mineralization, ALP activity, phosphorylated p38 and protein levels of BMP2, Runx2, ALP, Col-I and OC during osteogenesis. Overexpression and knockdown of Ddr1 in osteoblasts demonstrated that DDR1 mediates the expression and activity of Runx2 and the downstream osteogenesis markers during osteogenesis through regulation of p38 phosphorylation.
Project description:The discoidin domain receptors, DDR1 and DDR2, are nonintegrin collagen receptors that are members of the receptor tyrosine kinase family. Both DDRs bind a number of different collagen types and play important roles in embryo development. Dysregulated DDR function is associated with progression of various human diseases, including fibrosis, arthritis, and cancer. By interacting with key components of the extracellular matrix and displaying distinct activation kinetics, the DDRs form a unique subfamily of receptor tyrosine kinases. DDR-facilitated cellular functions include cell migration, cell survival, proliferation, and differentiation, as well as remodeling of extracellular matrices. This review summarizes the current knowledge of DDR-ligand interactions, DDR-initiated signal pathways and the molecular mechanisms that regulate receptor function. Also discussed are the roles of DDRs in development and disease progression.
Project description:Collagen is the most abundant component of tumor extracellular matrix (ECM). ECM collagens are known to directly interact with the tumor cells via cell surface receptor and play crucial role in tumor cell survival and promote tumor progression. Collagen receptor DDR1 is a member of receptor tyrosine kinase (RTK) family with a unique motif in the extracellular domain resembling Dictyostelium discoideum protein discoidin-I. DDR1 displays delayed and sustained activation upon interaction with collagen and recent findings have demonstrated that DDR1-collagen signaling play important role in cancer progression. In this review, we discuss the current knowledge on the role of DDR1 in cancer metastasis and possibility of a potential therapeutic approach of DDR1 targeted therapy in cancer.
Project description:Muskelin is an intracellular protein with a C-terminal kelch-repeat domain that was initially characterized as having functional involvement in cell spreading on the extracellular matrix glycoprotein thrombospondin-1. As one approach to understanding the functional properties of muskelin, we have combined bioinformatic and biochemical studies. Through analysis of a new dataset of eight animal muskelins, we showed that the N-terminal region of the polypeptide corresponds to a predicted discoidin-like domain. This domain architecture is conserved in fungal muskelins and reveals a structural parallel between the muskelins and certain extracellular fungal galactose oxidases, although the phylogeny of the two groups appears distinct. In view of the fact that a number of kelch-repeat proteins have been shown to self-associate, co-immunoprecipitation, protein pull-down assays and studies of cellular localization were carried out with wild-type, deletion mutant and point mutant muskelins to investigate the roles of the discoidin-like and kelch-repeat domains. We obtained evidence for cis- and trans-interactions between the two domains. These studies provide evidence that muskelin self-associates through a head-to-tail mechanism involving the discoidin-like domain.
Project description:Discoidin domain receptor tyrosine kinases (DDRs) are a class of receptor tyrosine kinases (RTKs), and their dysregulation is associated with multiple diseases (including cancer, chronic inflammatory conditions, and fibrosis). The DDR family members (DDR1a-e and DDR2) are widely expressed, with predominant expression of DDR1 in epithelial cells and DDR2 in mesenchymal cells. Structurally, DDRs consist of three regions (an extracellular ligand binding domain, a transmembrane domain, and an intracellular region containing a kinase domain), with their kinase activity induced by receptor-specific ligand binding. Collagen binding to DDRs stimulates DDR phosphorylation activating kinase activity, signaling to MAPK, integrin, TGF-β, insulin receptor, and Notch signaling pathways. Abnormal DDR expression is detected in a range of solid tumors (including breast, ovarian, cervical liver, gastric, colorectal, lung, and brain). During tumorigenesis, abnormal activation of DDRs leads to invasion and metastasis, via dysregulation of cell adhesion, migration, proliferation, secretion of cytokines, and extracellular matrix remodeling. Differential expression or mutation of DDRs correlates with pathological classification, clinical characteristics, treatment response, and prognosis. Here, we discuss the discovery, structural characteristics, organizational distribution, and DDR-dependent signaling. Importantly, we highlight the key role of DDRs in the development and progression of breast and ovarian cancer.
Project description:Development of the craniofacial skeleton requires interactions between progenitor cells and the collagen-rich extracellular matrix (ECM). The mediators of these interactions are not well-defined. Mutations in the discoidin domain receptor 2 gene (DDR2), which encodes a non-integrin collagen receptor, are associated with human craniofacial abnormalities, such as midface hypoplasia and open fontanels. However, the exact role of this gene in craniofacial morphogenesis is not known. As will be shown, Ddr2-deficient mice exhibit defects in craniofacial bones including impaired calvarial growth and frontal suture formation, cranial base hypoplasia due to aberrant chondrogenesis and delayed ossification at growth plate synchondroses. These defects were associated with abnormal collagen fibril organization, chondrocyte proliferation and polarization. As established by localization and lineage-tracing studies, Ddr2 is expressed in progenitor cell-enriched craniofacial regions including sutures and synchondrosis resting zone cartilage, overlapping with GLI1 + cells, and contributing to chondrogenic and osteogenic lineages during skull growth. Tissue-specific knockouts further established the requirement for Ddr2 in GLI +skeletal progenitors and chondrocytes. These studies establish a cellular basis for regulation of craniofacial morphogenesis by this understudied collagen receptor and suggest that DDR2 is necessary for proper collagen organization, chondrocyte proliferation, and orientation.