RESUMO
HLJ1 (DNAJB4), a DNAJ/Hsp40 chaperone, has emerged as a novel prognostic marker in lung cancers; however, the molecular contribution and functionality in neoplastic diseases remain to be established. This study demonstrated that HLJ1 inhibits epithelial-mesenchymal transition in vitro and reduces lung cancer metastasis in vivo. Using shRNA silencing and ectopic expression of HLJ1, we found that HLJ1 not only suppresses catalytic activity of Src but also downregulates the formation of oncogenic complexes associated with the EGFR, FAK and STAT3 signaling pathways. A screen of specimens from HLJ1-knockout mice and lung cancer patients validated that HLJ1 expression is inversely correlated with Src activity. Mechanistically, HLJ1 protein directly bound to catalytic and protein-binding domains of Src through its amino acid Y172 and the P301/P304 motif. Following Src-induced HLJ1 phosphorylation at Y172, HLJ1-Src interaction was elevated, resulting in Src inhibition and malignancy suppression. Interestingly, both Src-binding regions also occurred in other DNAJB family members and contributed to anti-invasive activities of DNAJB proteins. We conclude that HLJ1 is an endogenous Src inhibitor that can suppress cancer metastasis through complex interacting mechanisms. This HLJ1-Src complex might provide a promising molecular model for developing new anticancer strategies.
Assuntos
Proteínas de Choque Térmico HSP40/metabolismo , Neoplasias/metabolismo , Neoplasias/patologia , Quinases da Família src/antagonistas & inibidores , Sequência de Aminoácidos , Animais , Modelos Animais de Doenças , Progressão da Doença , Ativação Enzimática , Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Proteínas de Choque Térmico HSP40/química , Proteínas de Choque Térmico HSP40/genética , Proteínas de Choque Térmico HSP40/farmacologia , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patologia , Masculino , Camundongos , Camundongos Knockout , Modelos Biológicos , Modelos Moleculares , Mutação , Invasividade Neoplásica , Metástase Neoplásica , Neoplasias/genética , Ligação Proteica , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Interferência de RNA , RNA Interferente Pequeno/genética , Domínios de Homologia de src , Quinases da Família src/química , Quinases da Família src/metabolismoRESUMO
OBJECTIVE: To study postnatal cardiac differentiation in the mouse. HYPOTHESIS: There might be mechanisms or factors in cardiac differentiation that could be identified by systematic gene expression analysis during postnatal cardiac development. METHODS: Expression of 6144 genes was examined in mouse heart, from the newborn period (day 0), through day 7 and day 14 day, to adulthood, using the cDNA microarray approach. Northern blotting and immunohistochemical techniques were used to confirm the microarray results. RESULTS: Various cardiac development related genes involving the cell cycle (cyclin B1, proliferating cell nuclear antigen (PCNA), and Ki67), growth factors (IGF-II, pleiotrophin (PTN), and midkine (MK)), and transcriptional regulation, cytoskeleton, and detoxification enzymes were identified by microarray analysis. Some of these genes were also confirmed by Northern blotting and immunohistochemistry of their RNA and protein content. In vivo treatment with PTN (20 ng/g) increased bromodeoxyuridine incorporation (by 2.24-fold) and PCNA expression (by 1.71-fold) during day 7 to day 14, indicating that PTN induces cell proliferation in mouse heart. CONCLUSIONS: Global gene expression analysis in the whole heart may be useful in understanding the orchestrated process of postnatal development or terminal differentiation in the cardiac environment. These data are likely to be helpful in studying developmental anomalies of the heart in neonates.