Anti-CUL5 monoclonal antibody, clone FQS25836

Phosphorylation-dependent protein ubiquitylation and degradation provides an irreversible mechanism to terminate protein kinase signaling. Here, we report that mammary epithelial cells require cullin-5-RING-E3-ubiquitin-ligase complexes (Cul5-CRLs) to prevent transformation by a Src-Cas signaling pathway. Removal of Cul5 stimulates growth-factor-independent growth and migration, membrane dynamics and colony dysmorphogenesis, which are all dependent on the endogenous tyrosine kinase Src. Src is activated in Cul5-deficient cells, but Src activation alone is not sufficient to cause transformation. We found that Cul5 and Src together stimulate degradation of the Src substrate p130Cas (Crk-associated substrate). Phosphorylation stimulates Cas binding to the Cul5-CRL adaptor protein SOCS6 and consequent proteasome-dependent degradation. Cas is necessary for the transformation of Cul5-deficient cells. Either knockdown of SOCS6 or use of a degradation-resistant Cas mutant stimulates membrane ruffling, but not other aspects of transformation. Our results show that endogenous Cul5 suppresses epithelial cell transformation by several pathways, including inhibition of Src-Cas-induced ruffling through SOCS6.

Background: The objective of our study was to explore the characteristics of the regulatory network after siRNA-Sp1 (Specificity Protein 1) treatment in HeLa cells through the regulation network construction with bioinformatics methods. Materials and Methods: Using GSE37935 datasets downloaded from Gene Expression Omnibus data, the differentially expressed genes (DEGs) were screened out by the limma package in R software. Combining the DEGs with the data from the microRNA (miRNA) databases and transcription factor databases, an integrated regulatory network was established with Cytoscape. Then the motifs in the network were examined by FANMOD. Results: A total of 708 DEGs were screened, and a regulatory network consisting of 585 nodes and 1070 edges was constructed. By analyzing the two modules extracted from the network, we found that the most significant biological processes were cell cycle and apoptosis, some significant DEGs among them were CDKN1A, CUL5, and EGFR. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis discovered that DEGs, including EGFR, CDKN1A, RRM2B, and GADD45B, were significantly enriched in glioma pathway and p53 signaling pathway. Conclusion: While Sp1 was silenced by siRNA, the regulatory network in HeLa cells changed a lot. Genes related to cell cycle and apoptosis in the cell nucleus were dysregulated and the p53 signaling pathway was disturbed.