GP73 is a glucogenic hormone regulating SARS-CoV-2-induced hyperglycemia

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection induces new-onset diabetes and severe metabolic complications of pre-existing diabetes. The pathogenic mechanism underlying this is incompletely understood. Here, we provided evidence linking circulating GP73 with the exaggerated gluconeogenesis triggered by SARS-CoV-2 infection. We found that SARS-CoV-2 infection or glucotoxic condition increased the cellular secretion of GP73. Secreted GP73 trafficked to the liver and kidney to stimulate gluconeogenesis through cAMP/PKA pathway. By using global phosphoproteomics, we found a drastic remodeling of PKA kinase hub exerted by GP73. Notably, COVID-19 patients showed pathologically elevated plasma GP73, and neutralization of the secreted GP73 inhibited enhanced PKA signaling and glucose production associated with SARS-CoV-2 infection. GP73 blockade also reduced gluconeogenesis and lowered hyperglycemia in type 2 (T2D) diabetic mice. Therefore, our findings provide novel insight into the roles of GP73 as a key glucogenic hormone and mechanistic clues underlying the development of SARS-CoV-induced glucose abnormalities.

Closed-Loop Control between Two GTPase Switches makes the Secretory Functions of the Golgi Responsive to Growth Factors

Intercellular (between-cells) signals must be converted into an intracellular (within-cell) signal before it can trigger a proportionate response. How cells mount such proportionate responses within their interior remains unknown. Here we unravel the role of a coupled GTPase circuit on the Golgi membranes which enables the intracellular secretory machinery to respond proportionately to the growth factors in the extracellular space. The circuit, comprised of two species of biological switches, the Ras-superfamily monomeric GTPase Arf1, and the heterotrimeric GTPase, Giαβγ, and their corresponding GAPs and GEFs, is coupled via at least one a forward and two key negative feedback loops. Interrogation of the circuit featuring such closed-loop control (CLC) using an integrated systems-based and experimental approach showed that CLC allows the two GTPases to mutually control each other and convert the expected switch-like behavior of Arf1 into an unexpected dose-response aligned (DoRA) linear behavior. Such behavior translates into growth factor-stimulated Giαβγ activity on Golgi membranes, temporal finiteness of Arf1 activity, and cellular secretion that is proportional to the stimuli. Findings reveal the importance of the coupled GTPase circuit in rendering concordant cellular responses via the faithful transmission of growth signals to the secretory machinery.

Synthetic Cellular Communication-Based Screening for Strains with Improved 3-Hydroxypropionic Acid Secretion

Although cellular secretion is important in industrial biotechnology, its assessment is difficult due to the lack of efficient analytical methods. This study describes a synthetic cellular communication-based microfluidic platform for...

Analysis of SARS-CoV-2 spike glycosylation reveals shedding of a vaccine candidate

Severe acute respiratory syndrome coronavirus 2 is the causative pathogen of the COVID-19 pandemic which as of Nov 15, 2020 has claimed 1,319,946 lives worldwide. Vaccine development focuses on the viral trimeric spike glycoprotein as the main target of the humoral immune response. Viral spikes carry glycans that facilitate immune evasion by shielding specific protein epitopes from antibody neutralisation. Immunogen integrity is therefore important for glycoprotein-based vaccine candidates. Here we show how site-specific glycosylation differs between virus-derived spikes and spike proteins derived from a viral vectored SARS-CoV-2 vaccine candidate. We show that their distinctive cellular secretion pathways result in different protein glycosylation and secretion patterns, which may have implications for the resulting immune response and future vaccine design.

PSVI-4 Modulation of galectin gene expression and secretion in cow blood stimulated with Phorbol 12-myristate 13-acetate

The objective of this study was to assess the expression and secretion of galectin gene in cow blood stimulated with Phorbol 12-myristate 13-acetate (PMA). Phorbol 12-myristate 13-acetate is a phorbol diester that activates the enzyme protein kinase C (PKC). Activated PKC is associated with regulation of inflammation. Galectins (Gal) are β-galactoside binding proteins that modulate inflammation following intra and extra-cellular secretion. Blood was collected from the jugular vein of clinically healthy Holstein-Friesian cows (n = 3) from North Carolina A&T diary unit. Individual samples were treated with either 10ng/ml of PMA or Phosphate buffer saline (PBS) for 30 minutes at 370 C. Total RNA was isolated from blood, pooled and transcribed to cDNA, for real-time PCR. Cow specific primers LGALS -1, -2, -3, -4, -7, -8, -9, -12 were designed using the NCBI Primer 3 tool. Housekeeping genes RPLP0 and UCHL5 were used for normalization. Fold change was calculated using the Livak method (Fold change >2 were considered as significant). Secretion of GAL -1, -2, -3, -4, -8, -9 was assessed using bovine GAL specific ELISA kits. Data were analyzed by one-way ANOVA using SAS version 9.4. Treatment with PMA up regulated the transcription of LGALS -2, -4, -8, (2.28, 2.36, 2.39 folds respectively) and down regulated the transcription of LGALS -9 (-5.04 fold). Transcription of LGALS -1, -3, -7, 12 remained unchanged. All tested GAL were secreted. Treatment with PMA increased the secretion level of GAL -1, -3, -4 and decreased the secretion level of GAL -2, -4, -9 (P > 0.05). Thus, activation of PKC differentially modulates galectin gene expression and secretion in cow blood. The observed differences in treatment and control groups warrant further studies.