SNX27 suppresses SARS-CoV-2 infection by inhibiting viral lysosome/late endosome entry

After binding to its cell surface receptor angiotensin converting enzyme 2 (ACE2), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the host cell through directly fusing with plasma membrane (cell surface pathway) or undergoing endocytosis traveling to lysosome/late endosome for membrane fusion (endocytic pathway). However, the endocytic entry regulation by host cell remains elusive. Recent studies show ACE2 possesses a type I PDZ binding motif (PBM) through which it could interact with a PDZ domain-containing protein such as sorting nexin 27 (SNX27). In this study, we determined the ACE2-PBM/SNX27-PDZ complex structure, and, through a series of functional analyses, we found SNX27 plays an important role in regulating the homeostasis of ACE2 receptor. More importantly, we demonstrated SNX27, together with retromer complex (the core component of the endosomal protein sorting machinery), prevents ACE2/virus complex from entering lysosome/late endosome, resulting in decreased viral entry in cells where the endocytic pathway dominates. The ACE2/virus retrieval mediated by SNX27–retromer could be considered as a countermeasure against invasion of ACE2 receptor-using SARS coronaviruses.

Direct Inhibition of the First PDZ Domain of ZO-1 by Glycyrrhizin is a Possible Mechanism of Tight Junction Opening of Caco-2 Cells.

Glycyrrhizin (GL) is known to exhibit a variety of useful pharmacological activities, including anti-inflammation, anti-hepatotoxicity, and enhancement of intestinal drug absorption. GL has been reported to modify the assembly of...

Potential Role of CTNNA3 and FRMPD4 in Vascular Thrombosis of Colon Adenocarcinoma

Background: Vascular tumor thrombus is an important pathological feature of malignant tumors, closely related to lymph node metastasis, and considered to be tumor micrometastasis. Two down-regulated genes, Catenin Alpha 3 (CTNNA3) and FERM And PDZ Domain Containing 4 (FRMPD4) were selected via analyzing the differential expression of vascular tumor thrombus in colon adenocarcinoma and paracancerous tissues. Furthermore, we observed the potential role of them in vascular thrombosis of colon adenocarcinoma.Method: Candidate genes for vascular thrombosis of colon adenocarcinoma were screened by GSE127069, and then pan-cancer verification and immune infiltration analysis were performed. The relationship between gene and vascular thrombosis was analyzed from the level of gene mutation by cBioPortal. Finally, the clinical samples collected were used for expression verification.Results: CTNNA3 and FRMPD4 were low-expressed in vascular tumor thrombus of colon adenocarcinoma, which were positively correlated with microsatellite instability (MSI). They were also closely related to immune microenvironment and immune cell subtype infiltration. According to the analysis of gene mutation, their gene deletion was related to the vascular invasion indicator. Finally, the protein and mRNA expression of CTNNA3 and FRMPD4 were down-regulated in the samples of vascular thrombosis of colon adenocarcinoma, compared with the normal glands which from paracancerous tissues.Conclusion: Our study demonstrates that CTNNA3 and FRMPD4 may be potential biomarkers of vascular thrombosis in colon adenocarcinoma. These results may provide a new strategy to identify the micrometastasis in colon adenocarcinoma.

Atomic resolution Protein Allostery from the multi-state Structure of a PDZ Domain

Recent methodological advances in solution NMR allow the determination of multi-state protein structures and provide insights into correlated motion at atomic resolution as demonstrated here for the well-studied PDZ2 domain of protein human tyrosine phosphatase 1E for which protein allostery was predicted. Two-state protein structures were calculated for both the free form and in complex with the RA-GEF2 peptide using the exact nuclear Overhauser effect (eNOE) method. In the apo protein states an allosteric conformational preselection step comprising almost 60% of the domain was detected with an "open" ligand welcoming state and a "closed" state that obstructs the binding site by the distance between the β-sheet, α-helix 2 and sidechains of residues Lys38 and Lys72. Observed apo-holo structural rearrangements of induced fit-type are in line with previously published evolution-based analysis covering ~25% of the domain with only a partial overlap with the protein allostery of the open form. These presented structural studies highlight the presence of a dedicated highly optimized dynamic interplay of the complexity of the PDZ2 domain owed by the structure-dynamics landscape.

Afadin couples RAS GTPases to the polarity rheostat Scribble

AFDN/Afadin is required for establishment and maintenance of cell-cell contacts and is a unique effector of RAS GTPases. The biological consequences of RAS signalling to AFDN are unknown. Here, we use proximity-based proteomics to generate an interaction map for the long and short isoforms of AFDN, identifying the polarity protein SCRIB/Scribble as the top hit. We reveal that the first PDZ domain of SCRIB and the AFDN FHA domain mediate a direct but non-canonical interaction between these important adhesion and polarity proteins. Further, the dual RA domains of AFDN have broad specificity for RAS and RAP GTPases, and KRAS co-localizes with and promotes AFDN-SCRIB complex formation. Knockout of AFDN or SCRIB in MCF7 epithelial cells disrupts MAPK and PI3K activation and inhibits cell motility in a growth factor-dependent manner. These data have important implications for understanding why cells with activated RAS have reduced cell contacts and polarity defects, and finally begin to characterize AFDN as a RAS effector.

Modulation of hippocampal network oscillation by PICK1-dependent cell surface expression of mGlu3 receptors

mGlu3 receptors control the sleep/wake architecture which plays a role in the glutamatergic pathophysiology of schizophrenia. Interestingly, mGlu3 receptors expression is decreased in the brain of schizophrenic patients. However, little is known about the molecular mechanisms regulating mGlu3 receptors at the cell membrane. Subcellular receptor localization is strongly dependent on protein-protein interactions. Here we show that mGlu3 interacts with PICK1 and that their binding is important for receptor surface expression and function. Disruption of their interaction via an mGlu3 C-terminal mimicking peptide or an inhibitor of the PDZ domain of PICK1 altered the functional expression of mGlu3 receptors. Consequently, we investigated whether disruption of the mGlu3-PICK1 interaction affects hippocampal theta oscillations in vitro and in vivo. We found a decreased frequency of theta oscillations in organotypic hippocampal slices, similar to what previously observed in mGlu3 -/- mice. In addition, hippocampal theta power was reduced during REM sleep, NREM sleep and wake states after intra-ventricular administration of the mGlu3 C-terminal mimicking peptide. Targeting the mGlu3-PICK1 complex could thus be relevant to the pathophysiology of schizophrenia.

Decoding the Role of DVL1 in Intracranial Meningioma

In the search for molecular candidates for targeted meningioma therapies, increasing attention has been paid to the role of signaling pathways in the development and progression of intracranial meningiomas. Although it is well known that the Wnt signaling pathway is involved in meningioma progression, the role of its central mediator, DVL1, is still unclear. In order to investigate the influence of DVL1 gene alterations on the progression of human intracranial meningioma, we focused on its central PDZ domain, which is responsible for DVL interaction with the Fzd receptor and the phosphorylation of DVL mediated through the casein kinases CK1 and CK2. A genetic analysis of genomic instability revealed the existence of microsatellite instability in 9.09% and the loss of heterozygosity in 6.06% of the samples. The sequencing of the PDZ gene region showed repetitive deletions of two bases located in intron 7 and exon 8, and a duplication in intron 8 in most samples, with different outcomes on the biological function of the DVL1 protein. Immunohistochemistry revealed that the nuclear expression of DVL1 was significantly correlated with a higher expression of active β-catenin (p = 0.029) and a higher meningioma grade (p = 0.030), which leads to the conclusion that it could be used as biomarker for meningioma progression and the activation of the Wnt signaling pathway.

A phosphoregulated RhoGEF feedback loop tunes cortical flow driven amoeboid migration in vivo

Cortical flow driven amoeboid migration utilizes friction from retrograde cortical actin flow to generate motion. Many cell types, including cancer cells, can assemble a cortical flow engine to migrate under confinement and low adhesion in vitro, but it remains unclear whether this engine is endogenously utilized in vivo. Moreover, in the context of a changing environment, it is not known how upstream regulation can set in motion and sustain a mutual feedback between flow and polarity. Here, we establish that Drosophila primordial germ cells (PGCs) utilize cortical flow driven amoeboid migration and that flows are oriented by external cues during developmental homing in vivo. The molecular basis of flow modulation is a phosphoregulated feedback loop involving RhoGEF2, a microtubule plus-end tracking RhoA specific RhoGEF, enriched at the rear of PGCs. RhoGEF2 depletion slows and disorganizes cortical flow, reducing migration speed, while RhoGEF2 activation accelerates cortical flow, thereby augmenting myosin II polarity and migration speed. Both perturbations impair PGC pathfinding, suggesting cortical flows must be tuned for accurate guidance. We surprisingly find that RhoGEF2 polarity and activation are independent of upstream canonical Gα12/13 signaling. Instead, its PDZ domain and conserved RhoA binding residues in its PH domain are required to establish a positive feedback loop that augments its basal activity. Upstream regulation of this feedback loop occurs via AMPK dependent multisite phosphorylation near a conserved EB1 binding SxIP motif, which releases RhoGEF2 from EB1 dependent inhibition. Thus, we reveal cortical flows as versatile, tunable engines for directed amoeboid migration in vivo.

Effect of tumor-associated macrophages on lncRNA PURPL/miR-363/PDZD2 axis in osteosarcoma cells

Tumor-associated macrophages (TAMs) are known to participate in osteosarcoma (OS) progression. As demonstrated in our previous research, miR-363 played a tumor inhibitory effect in OS cells via lowering the PDZ domain containing 2 (PDZD2) expression. The regulatory roles of TAMs on miR-363/PDZD2 and the internal mechanism relating to long noncoding RNA p53 upregulated regulator of P53 levels (lncRNA PURPL) are examined in this study. TAM-like macrophages were formed by inducing CD14+ peripheral blood mononuclear cells (PBMCs). The TAMs migration was detected after MG-63 cells transfected with miR-363 mimics or inhibitors. We then analyzed the regulatory activity of PURPL on miR-363 expression. We also tested the influences of PURPL overexpression/knockdown on MG-63 cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT), as well as TAMs migration. Silence in PDZD2 expression was used to confirm the effects of PURPL on MG-63 cells. We successfully induced TAM-like macrophages. MG-63 cells transfecting miR-363 mimics suppressed TAMs migration while transfecting a converse effect was seen in miR-363 inhibitor. TAMs raised PURPL expression in MG-63 cells, which was an upstream regulator of miR-363. Along with TAMs migration, PURPL overexpression promoted MG-63 cell proliferation, migration, invasion, and EMT. An opposite influence was seen due to the PURPL knockdown. The silence of PDZD2 weakened the influences of PURPL overexpression on MG-63 cells and TAMs migration. On modulating the PURPL/miR-363/PDZD2 axis, TAMs-promoted OS development might be achieved.