A cardiotoxicity-eliminated ACE2 variant as a pan-inhibitor against coronavirus cell invasion.

Human recombinant ACE2 (hrACE2) has been highly anticipated as a successful COVID-19 treatment; however, its potential to cause cardiac side effects has given rise to many concerns. Here, we developed a cardiotoxicity-eliminated hrACE2 variant, which had four mutation sites within hrACE2 (H345L, H374L, H378L, H505L) and was named as hrACE2-4mu. hrACE2-4mu has a consistent binding affinity with the variant SARS-CoV-2 spike proteins (SPs) and an efficient ability to block SP-induced SARS-CoV-2 entry into cells. In golden hamsters, injection of purified wild-type (WT) hrACE2 rescues the early stages of pneumonia caused by the SPs of the WT, delta, and omicron variants with reduced inflammatory cell infiltration. However, long-term injection of WT hrACE2 induces undesired cardiac fibrosis, as demonstrated by upregulated fibronectin and collagen expression. Our newly developed hrACE2-4mu showed similar protective abilities against a series of coronavirus cell invasions as WT hrACE2, meanwhile it did not cause apparent cardiac side effects. Thus, we generated a cardiotoxicity-eliminated variant of hrACE2 as a pan-inhibitor against coronavirus cell invasion, providing a potential novel strategy for the treatment of COVID-19 and other coronaviruses.

RNA-binding protein DDX1 is responsible for fatty acid-mediated repression of insulin translation.

The molecular mechanism in pancreatic ß cells underlying hyperlipidemia and insulin insufficiency remains unclear. Here, we find that the fatty acid-induced decrease in insulin levels occurs due to a decrease in insulin translation. Since regulation at the translational level is generally mediated through RNA-binding proteins, using RNA antisense purification coupled with mass spectrometry, we identify a novel insulin mRNA-binding protein, namely, DDX1, that is sensitive to palmitate treatment. Notably, the knockdown or overexpression of DDX1 affects insulin translation, and the knockdown of DDX1 eliminates the palmitate-induced repression of insulin translation. Molecular mechanism studies show that palmitate treatment causes DDX1 phosphorylation at S295 and dissociates DDX1 from insulin mRNA, thereby leading to the suppression of insulin translation. In addition, DDX1 may interact with the translation initiation factors eIF3A and eIF4B to regulate translation. In high-fat diet mice, the inhibition of insulin translation happens at an early prediabetic stage before the elevation of glucose levels. We speculate that the DDX1-mediated repression of insulin translation worsens the situation of insulin resistance and contributes to the elevation of blood glucose levels in obese animals.

Publisher Correction: Optimizing the fragment complementation of APEX2 for detection of specific protein-protein interactions in live cells.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Author Correction: Optimizing the fragment complementation of APEX2 for detection of specific protein-protein interactions in live cells.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Optimizing the fragment complementation of APEX2 for detection of specific protein-protein interactions in live cells.

Dynamic protein-protein interactions (PPIs) play crucial roles in cell physiological processes. The protein-fragment complementation (PFC) assay has been developed as a powerful approach for the detection of PPIs, but its potential for identifying protein interacting regions is not optimized. Recently, an ascorbate peroxidase (APEX2)-based proximity-tagging method combined with mass spectrometry was developed to identify potential protein interactions in live cells. In this study, we tested whether APEX2 could be employed for PFC. By screening split APEX2 pairs attached to FK506-binding protein 12 (FKBP) and the FKBP12-rapamycin binding (FRB) domain, which interact with each other only in the presence of rapamycin, we successfully obtained an optimized pair for visualizing the interaction between FRB and FKBP12 with high specificity and sensitivity in live cells. The robustness of this APEX2 pair was confirmed by its application toward detecting the STIM1 and Orial1 homodimers in HEK-293 cells. With a subsequent mass spectrometry analysis, we obtained five different biotinylated sites that were localized to the known interaction region on STIM1 and were only detected when the homodimer formed. These results suggest that our PFC pair of APEX2 provides a potential tool for detecting PPIs and identifying binding regions with high specificity in live cells.

HID-1 is required for homotypic fusion of immature secretory granules during maturation.

Secretory granules, also known as dense core vesicles, are generated at the trans-Golgi network and undergo several maturation steps, including homotypic fusion of immature secretory granules (ISGs) and processing of prehormones to yield active peptides. The molecular mechanisms governing secretory granule maturation are largely unknown. Here, we investigate a highly conserved protein named HID-1 in a mouse model. A conditional knockout of HID-1 in pancreatic ß cells leads to glucose intolerance and a remarkable increase in the serum proinsulin/insulin ratio caused by defective proinsulin processing. Large volume three-dimensional electron microscopy and immunofluorescence imaging reveal that ISGs are much more abundant in the absence of HID-1. We further demonstrate that HID-1 deficiency prevented secretory granule maturation by blocking homotypic fusion of immature secretory granules. Our data identify a novel player during the early maturation of immature secretory granules.

A new dimethyl labeling-based SID-MRM-MS method and its application to three proteases involved in insulin maturation.

The absolute quantification of target proteins in proteomics involves stable isotope dilution coupled with multiple reactions monitoring mass spectrometry (SID-MRM-MS). The successful preparation of stable isotope-labeled internal standard peptides is an important prerequisite for the SID-MRM absolute quantification methods. Dimethyl labeling has been widely used in relative quantitative proteomics and it is fast, simple, reliable, cost-effective, and applicable to any protein sample, making it an ideal candidate method for the preparation of stable isotope-labeled internal standards. MRM mass spectrometry is of high sensitivity, specificity, and throughput characteristics and can quantify multiple proteins simultaneously, including low-abundance proteins in precious samples such as pancreatic islets. In this study, a new method for the absolute quantification of three proteases involved in insulin maturation, namely PC1/3, PC2 and CPE, was developed by coupling a stable isotope dimethyl labeling strategy for internal standard peptide preparation with SID-MRM-MS quantitative technology. This method offers a new and effective approach for deep understanding of the functional status of pancreatic ß cells and pathogenesis in diabetes.

Macrophage inhibitory cytokine 1 (MIC-1/GDF15) as a novel diagnostic serum biomarker in pancreatic ductal adenocarcinoma.

BACKGROUND: Macrophage inhibitory cytokine 1 (MIC-1/GDF15) has been identified as a potential novel biomarker for detection of pancreatic cancer (PCa). However, the diagnostic value of serum MIC-1 for pancreatic ductal adenocarcinoma (PDAC), particularly for those at the early stage, and the value for treatment response monitoring have not yet been investigated. METHODS: MIC-1 expression in tumor tissue was analyzed by RT-PCR from 64 patients with PDAC. Serum MIC-1 levels were detected by ELISA in 1472 participants including PDAC, benign pancreas tumor, chronic pancreatitis and normal controls. The diagnostic performance of MIC-1 was assessed and compared with CA19.9, CEA and CA242, and the value of it as a predictive indicator for therapeutic response and tumor recurrence was also evaluated. RESULTS: MIC-1 levels were significantly elevated in PDAC tissues as well as serum samples. The sensitivity of serum MIC-1 for PDAC diagnosis was much higher than that of CA19.9 (65.8% vs. 53.3%) with similar specificities. Furthermore, serum MIC-1 detected 238 out of 377 (63.1%) CA19.9-negative PDAC. Moreover, receiver operating characteristic (ROC) curve analysis also showed that serum MIC-1 had a better performance compared with CA19.9 in distinguishing early-stage PDAC from normal serum with a higher sensitivity (62.5% vs. 25.0% respectively). Notably, serum MIC-1 level was significantly decreased in patients with PDAC after curative resection and returned to elevated levels when tumor relapse occurred. CONCLUSIONS: Serum MIC-1 is significantly elevated in most PDAC, including those with negative CA19.9 and early stage disease, and thus may serve as a novel diagnostic marker in early diagnosis and postoperative monitoring of PDAC.

[Experimental study on antitumor effects of Shen Qi Jin Kang (SQJK)].

BACKGROUND & OBJECTIVE: SHEN QI JIN KANG (SQJK) capsule is a complex preparation, consisting of effective components extracted from radix astragali, ginseng, curcuma, etc. It has been demonstrated to be able to decrease tumor volume, increase life quality and prolong survival time in clinic application. The study was to investigate the antitumor effects of SQJK capsule in vivo and in vitro, and further explore the possible mechanisms. METHODS: The proliferation of cancer cells treated with SQJK was measured by MTT assay in twelve cell lines; cell apoptosis was observed under an electric microscopic and detected by flow cytometry in MCF-7 and MA891 cells; altered telomerase activity in A549 cells was examined by a telomerase activity detection kit. Furthermore, the inhibitory effect of SQJK on tumors was also surveyed in vivo by using mice and nude mice models bearing transplanted tumors. RESULTS: Inhibitory concentration 50% (IC(50)) of SQJK on A549, U251, MCF-7, Ketr-3, EJ, and A2780 cells was 30.954 microg/ml, 31.746 microg/ml, 37.220 microg/ml, 40.366 microg/ml, 41.398 microg/ml, and 45.083 microg/ml, respectively. Typical sub-G1 peaks, indicating the occurrence of apoptosis, were revealed in MA891and MCF-7 cells treated with SQJK. Morphological changes including cell shrinkage and condensation of chromosomes were observed. The telomerase activity of A549 was inhibited after 48 h of SQJK treatment. SQJK 1.8 g/kg inhibited the weights of transplanted tumors (MA891, H22, S180 in mice and PC-3 (M), MCF-7 and Ketr-3 in nude mice) by 50.84%, 48.91%, 40.88%, 62.50%, 47.83% and 30.06%, while SQJK 3.6 g/kg inhibited the weights by 56.49%, 59.62%, 55.70%, 70.76%, 58.66% and 50.18%, respectively. CONCLUSION: SQJK has demonstrated antitumor bioactivity both in vitro and in vivo, which may be related to its effects of inducing apoptosis and decreasing telomerase activity.