GPCR Kinase (GRK)-2 Is a Key Negative Regulator of Itch: l-Glutamine Attenuates Itch via a Rapid Induction of GRK2 in an ERK-Dependent Way

Gamma-Glutamyl Transferase: A Friend against Cholestatic Itch? A Retrospective Observational Data Analysis in Patients with Extrahepatic Cholestasis

Methods

We included 235 patients with chronic extrahepatic cholestasis due to pancreatic cancer, cholangiocarcinoma, or papillary carcinoma.

Results

GGT was significantly higher in patients without pruritus (median 967, IQR 587-1571) compared to patients with pruritus (median 561 IQR 266-1084 IU/l) (p < 0.01). In contrast, median alkaline phosphatase (AP) was 491 U/L (IQR; 353-684) in patients with pruritus and was not significantly different from 518 U/L (IQR; 353-726) in patients without pruritus (p = 0.524). Direct bilirubin was significantly higher in patients with pruritus compared to patients without pruritus (168 μmol/L (IQR; 95-256) vs. 120 μmol/L (IQR; 56.75-185.5)) (p < 0.01). After correcting for the extent of cholestasis via direct bilirubin, the negative association between GGT and pruritus remained significant and became stronger (p < 0.001).

Conclusion

Serum GGT activity is inversely associated with the presence of cholestatic itch in patients with chronic extrahepatic cholestasis.

Neddylation inhibition induces glutamine uptake and metabolism by targeting CRL3SPOP E3 ligase in cancer cells

Abnormal neddylation activation is frequently observed in human cancers and neddylation inhibition has been proposed as a therapy for cancer. Here, we report that MLN4924, a small-molecule inhibitor of neddylation activating enzyme, increases glutamine uptake in breast cancer cells by causing accumulation of glutamine transporter ASCT2/SLC1A5, via inactivation of CRL3-SPOP E3 ligase. We show the E3 ligase SPOP promotes ASCT2 ubiquitylation, whereas SPOP itself is auto-ubiquitylated upon glutamine deprivation. Thus, SPOP and ASCT2 inversely regulate glutamine uptake and metabolism. SPOP knockdown increases ASCT2 levels to promote growth which is rescued by ASCT2 knockdown. Adding ASCT2 inhibitor V-9302 enhances MLN4924 suppression of tumor growth. In human breast cancer specimens, SPOP and ASCT2 levels are inversely correlated, whereas lower SPOP with higher ASCT2 predicts a worse patient survival. Collectively, our study links neddylation to glutamine metabolism via the SPOP-ASCT2 axis and provides a rational drug combination for enhanced cancer therapy.

Neddylation inhibition has been reported as a therapy for cancer. Here, the authors show that neddylation inhibition increases glutamine metabolism by stabilizing glutamine transporter ASCT2, therefore targeting ASCT2 improves the anti-cancer effect of neddylation inhibitors.

Glutamine deficiency shifts the asthmatic state toward neutrophilic airway inflammation

Background

The administration of L‐glutamine (Gln) suppresses allergic airway inflammation via the rapid upregulation of MAPK phosphatase (MKP)‐1, which functions as a negative regulator of inflammation by deactivating p38 and JNK mitogen‐activated protein kinases (MAPKs). However, the role of endogenous Gln remains to be elucidated. Therefore, we investigated the mechanism by which endogenous Gln regulates MKP‐1 induction and allergic airway inflammation in an ovalbumin‐based murine asthma model.

Methods

We depleted endogenous Gln levels using L‐γ‐glutamyl‐p‐nitroanilide (GPNA), an inhibitor of the Gln transporter ASCT2 and glutamine synthetase small interfering siRNA. Lentivirus expressing MKP‐1 was injected to achieve overexpression of MKP‐1. Asthmatic phenotypes were assessed using our previously developed ovalbumin‐based murine model, which is suitable for examining sequential asthmatic events, including neutrophil infiltration. Gln levels were analyzed using a Gln assay kit.

Results

GPNA or glutamine synthetase siRNA successfully depleted endogenous Gln levels. Importantly, homeostatic MKP‐1 induction did not occur at all, which resulted in prolonged p38 MAPK and cytosolic phospholipase A₂ (cPLA₂) phosphorylation in Gln‐deficient mice. Gln deficiency augmented all examined asthmatic reactions, but it exhibited a strong bias toward increasing the neutrophil count, which was not observed in MKP‐1‐overexpressing lungs. This neutrophilia was inhibited by a cPLA₂ inhibitor and a leukotriene B4 inhibitor but not by dexamethasone.

Conclusion

Gln deficiency leads to the impairment of MKP‐1 induction and activation of p38 MAPK and cPLA₂, resulting in the augmentation of neutrophilic, more so than eosinophilic, airway inflammation.

SH2 domain-containing protein tyrosine phosphatase-2 (SHP-2) prevents cardiac remodeling after myocardial infarction through ERK/SMAD signaling pathway

In this study, we aimed to investigate the role of SH2 domain-containing protein tyrosine phosphatase-2 (SHP-2) in cardiac remodeling after myocardial infarction (MI) and explore the underlying molecular mechanism. MI model was established by ligation of the left anterior descending coronary artery. C57/BL6J mice were randomly administered with 3.0 mg/kg/day PHPS1 (PHPS1-treated group) or normal saline (model group) by intraperitoneal injection. After 4 weeks of infusion, the effects of PHPS1 on cardiac remodeling were evaluated. Echocardiography results showed that PHPS1 treatment aggravated the MI-induced deterioration of cardiac function, with worse cardiac function parameters. PHPS1 treatment significantly increased the infarcted area, as well as the fibrotic area and the expression of collagen I and collagen III. Western blots and immunofluorescence staining showed that PHPS1 treatment up-regulated the expression of p-GRK2, p-SMAD2/3 and p-ERK1/2, while U0126 reversed the effect of PHPS1. The present study indicated that PHPS1 treatment contributed to myocardial fibrosis and infarction by activating ERK/SMAD signaling pathway, suggesting that SHP-2 may be a promising treatment target for cardiac remodeling after MI.