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Tripartite motif‐containing protein 21 (TRIM21), identified as both a cytosolic E3 ubiquitin ligase and FcR (Fragment crystallizable receptor), primarily interacts with proteins via its PRY/SPRY domains and promotes their proteasomal degradation to regulate intracellular immunity. But how TRIM21 involves in intracellular immunity still lacks systematical understanding. Herein, it is probed into the TRIM21‐related literature and raises an interacting model about how TRIM21 orchestrates proteins in cytosol. In this novel model, TRIM21 generally interacts with miscellaneous protein in intracellular immunity in two ways: For one, TRIM21 solely plays as an E3, ubiquitylating a glut of proteins that contain specific interferon‐regulatory factor, nuclear transcription factor kappaB, virus sensors and others, and involving inflammatory responses. For another, TRIM21 serves as both E3 and specific FcR that detects antibody‐complexes and facilitates antibody destroying target proteins. Correspondingly delineated as Fc‐independent signaling and Fc‐dependent signaling in this review, how TRIM21's interactions contribute to intracellular immunity, expecting to provide a systematical understanding of this important protein and invest enlightenment for further research on the pathogenesis of related diseases and its prospective application is elaborated. [ABSTRACT FROM AUTHOR]

[Display omitted] • ARF1 is upregulated in both metastatic CRC and vemurafenib-resistant CRC cells. • ARF1 promotes CRC metastasis and vemurafenib resistance by interacting with IQGAP1. • ARF1-IQGAP1 interaction induces ERK pathway reactivation in vemurafenib resistance. • LY2839219 suppresses CRC metastasis by disturbing ARF1-IQGAP1 interaction. • Combination of LY2835219 and vemurafenib is a promising strategy for CRC treatment. Acquired resistance to BRAF inhibitor vemurafenib is frequently observed in metastatic colorectal cancer (CRC), and it is a thorny issue that results in treatment failure. As adaptive responses for vemurafenib treatment, a series of cellular bypasses are response for the adaptive feedback reactivation of ERK signaling, which warrant further investigation. We identified ARF1 (ADP-ribosylation factor 1) as a novel regulator of both vemurafenib resistance and cancer metastasis, its molecular mechanism and potential inhibitor were investigated in this study. DIA-based quantitative proteomics and RNA-seq were performed to systematic analyze the profiling of vemurafenib-resistant RKO cells (RKO-VR) and highly invasive RKO cells (RKO-I8), respectively. Co‑immunoprecipitation assay was performed to detect the interaction of ARF1 and IQGAP1 (IQ-domain GTPase activating protein 1). An ELISA-based drug screen system on FDA-approved drug library was established to screen the compounds against the interaction of ARF1-IQGAP1.The biological functions of ARF1 and LY2835219 were determined by transwell, western blotting, Annexin V-FITC/PI staining and in vivo experimental metastasis assays. We found that ARF1 strongly interacted with IQGAP1 to activate ERK signaling in VR and I8 CRC cells. Deletion of IQGAP1 or inactivation of ARF1 (ARF-T48S) restored the invasive ability induced by ARF1. As ARF1-IQGAP1 interaction is essential for ERK activation, we screened LY2835219 as novel inhibitor of ARF1-IQGAP1 interaction, which inactivated ERK signaling and suppressed CRC metastasis and vemurafenib-resistance in vitro and in vivo with no observed side effect. Furthermore, LY2835219 in combined treatment with vemurafenib exerted significantly inhibitory effect on ARF1-mediated cancer metastasis than used independently. This study uncovers that ARF1-IQGAP1 interaction-mediated ERK signaling reactivation is critical for vemurafenib resistance and cancer metastasis, and that LY2835219 is a promising therapeutic agent for CRC both as a single agent and in combination with vemurafenib. [ABSTRACT FROM AUTHOR]

Background CpxR is a critical regulator in bacterial adaptation to various harmful stresses, and is known to regulate bacterial resistance to commonly used antibiotics, such as aminoglycosides, β-lactams and polypeptides. However, the detailed study of functional residues of CpxR remains insufficient. Objectives To investigate the contribution of Lys219 to CpxR's function in regulating antibiotic resistance of Escherichia coli. Methods We performed sequence alignment and conservative analysis of the CpxR protein and constructed mutant strains. We then performed electrophoretic mobility shift assay, real-time quantitative PCR assay, determination of reactive oxygen species (ROS) levels, molecular dynamics simulation, conformational analysis and circular dichroism. Results All mutant proteins (K219Q, K219A and K219R) lost the cpxP DNA-binding ability. Additionally, the three complemented strains eK219A , eK219Q , and eK219R exhibited lower resistance to copper toxicity and alkaline pH toxicity than eWT. Molecular dynamics analysis revealed that mutation of Lys219 leads to looser and more unstable conformation of CpxR, leading to its decreased binding affinity with downstream genes. Moreover, the Lys219 mutation resulted in the down-regulation of efflux pump genes (acrD , tolC , mdtB and mdtA), leading to the accumulation of antibiotics inside the cells and an increase in ROS production, which significantly reduces antibiotic resistance. Conclusions The mutation of the key residue Lys219 causes a conformational change that results in the loss of regulatory ability of CpxR, which may potentially reduce to antibiotic resistance. Therefore, this study suggests that targeting the highly conserved sequence of CpxR could be a promising strategy for the development of new antibacterial drugs. [ABSTRACT FROM AUTHOR]