Geranylgeranyl Diphosphate Synthase Modulates Fetal Lung Branching Morphogenesis Possibly through Controlling K-Ras Prenylation

Lung patterning: Is a distal-to-proximal gradient of cell allocation and fate decision a general paradigm?: A gradient of distal-to-proximal distribution and differentiation of tip progenitors produces distinct compartments in the lung

Recent studies support a model in which the progeny of SOX9+ epithelial progenitors at the distal tip of lung branches undergo cell allocation and differentiation sequentially along the distal-to-proximal axis. Concomitant with the elongation and ramification of lung branches, the descendants of the distal SOX9+ progenitors are distributed proximally, express SOX2, and differentiate into cell types in the conducting airways. Amid subsequent sacculation, the distal SOX9+ progenitors generate alveolar epithelial cells to form alveoli. Sequential cell allocation and differentiation are integrated with the branching process to generate a functional branching organ. This review focuses on the roles of SOX9+ cells as precursors for new branches, as the source of various cell types in the conducting airways, and as progenitors of the alveolar epithelium. All of these processes are controlled by multiple signaling pathways. Many mouse mutants with defective lung branching contain underlying defects in one or more steps of cell allocation and differentiation of SOX9+ progenitors. This model provides a framework to understand the molecular basis of lung phenotypes and to elucidate the molecular mechanisms of lung patterning. It builds a foundation on which comparing and contrasting the mechanisms employed by different branching organs in diverse species can be made.

The prognostic role and metabolic function of GGPS1 in oral squamous cell carcinoma

Background: GGPS1(geranylgeranyl diphosphate synthase 1) is a member of the prenyltransferase family. Abnormal expression of GGPS1 can disrupt the balance between protein farnesylation and geranylgeranylation, thereby affecting a variety of cellular physiologic and pathological processes. However, it is still unknown how this gene could contribute to the prognosis of oral squamous cell carcinoma (OSCC). This study aimed to explore the prognostic role of GGPS1 in OSCC and its relationship with clinical features. Methods: The RNA-seq data and clinical data were obtained from TCGA. The survival analyses, Cox regression analyses, ROC curves, nomograms, calibration curves, and gene function enrichments were established by R software. Results: The results showed that the high expression of GGPS1 in OSCC is related to poor prognosis. At the same time, multivariate Cox regression analyses showed that GGPS1 could be an independent prognostic biomarker, and its gene expression level is closely related to the histological stage of cancer. GGPS1 may promote tumorigenesis because of its metabolic function. Conclusion: This study came to a conclusion that GGPS1, whose high expression has a significantly unfavorable meaning toward the prognosis of OSCC, can act as a novel independent biomarker for OSCC.

Potential biomarkers for inflammatory response in acute lung injury

Acute lung injury (ALI) is a severe respiratory disorder occurring in critical care medicine, with high rates of mortality and morbidity. This study aims to screen the potential biomarkers for ALI. Microarray data of lung tissues from lung-specific geranylgeranyl pyrophosphate synthase large subunit 1 knockout and wild-type mice treated with lipopolysaccharide were downloaded. Differentially expressed genes (DEGs) between ALI and wild-type mice were screened. Functional analysis and the protein-protein interaction (PPI) modules were analyzed. Finally, a miRNA-transcription factor (TF)-target regulation network was constructed. Totally, 421 DEGs between ALI and wild-type mice were identified. The upregulated DEGs were mainly enriched in the peroxisome proliferator-activated receptor signaling pathway, and fatty acid metabolic process, while downregulated DEGs were related to cytokine-cytokine receptor interaction and regulation of cytokine production. Cxcl5, Cxcl9, Ccr5, and Cxcr4 were key nodes in the PPI network. In addition, three miRNAs (miR505, miR23A, and miR23B) and three TFs (PU1, CEBPA, and CEBPB) were key molecules in the miRNA-TF-target network. Nine genes including ADRA2A, P2RY12, ADORA1, CXCR1, and CXCR4 were predicted as potential druggable genes. As a conclusion, ADRA2A, P2RY12, ADORA1, CXCL5, CXCL9, CXCR1, and CXCR4 might be novel markers and potential druggable genes in ALI by regulating inflammatory response.

Geranylgeranyl diphosphate synthase 1 knockdown suppresses NLRP3 inflammasome activity via promoting autophagy in sepsis-induced acute lung injury

BACKGROUND

NOD-like receptor protein 3 (NLRP3) inflammasome activation has emerged as a crucial contributor to sepsis-induced lung injury. Geranylgeranyl diphosphate synthase 1 (GGPPS1) reportedly exerts the pro-inflammatory capability via activation of NLRP3 inflammasome. However, little is known about the role and mechanism of GGPPS1 in sepsis-induced lung injury.

METHODS

Mice underwent cecal ligation and puncture (CLP) surgery to establish the in vivo model of sepsis. The lung injury of mice was assessed by analyzing the histological changes, the lung wet/dry ratio, PaO2/FiO2 ratio, myeloperoxidase (MPO) activity, total protein content, total cell, and polymorphonuclear leukocyte counts. Mouse alveolar macrophages MH-S were exposed to LPS for developing in vitro model of sepsis. The mRNA and protein expression levels of GGPPS1, beclin-1, and autophagy and inflammasome-related genes were detected using quantitative reverse transcription-polymerase chain reaction and western blot assays. Enzyme-linked immunosorbent assay was conducted to determine the levels of interleukin (IL)-1β and IL-18.

RESULTS

We successfully established sepsis-induced acute lung injury in vivo by CLP surgery. GGPPS1 was upregulated in the lung tissues of CLP-induced septic mice. The activation of autophagy and NLRP3 inflammasome were found in the lung tissues of CLP-induced septic mice. The addition of exogenous GGPP (synthesis products catalyzed by GGPPS1) and autophagic inhibitor 3-MA aggravated sepsis-induced hypoxemia, alveolar inflammatory response, intrapulmonary hemorrhage, and pulmonary edema, as evidenced by increased lung injury score, lung wet/dry weight ratio, MPO activity, total protein content, total cell, and PMNs counts, and decreased PaO2/FiO2 ratio. While NLRP3 inhibitor MCC950 exerted the opposite effects. Additionally, administration of exogenous GGPP could inhibit the activation of autophagy, enhance the activity of NLRP3 inflammasome, and the production of IL-1β and IL-18. Inhibition of autophagy by 3-MA treatment also promoted the activity of NLRP3 inflammasome and the production of IL-1β and IL-18. While MCC950 restrained the activity of NLRP3 inflammasome, but did not affect the activation of autophagy. Notably, the expression of GGPPS1 was unaltered in CLP-induced mice following GGPP, 3-MA, or MCC950 treatment. Moreover, GGPPS1 was upregulated in MH-S cells stimulated with LPS, and GGPPS1 knockdown enhanced the activation of autophagy and inhibited the activity of NLRP3 inflammasome in vitro. Importantly, depletion of GGPPS1 could alleviate LPS-induced inflammatory response by inducing autophagy-dependent NLRP3 inflammasome inhibition.

CONCLUSION

GGPPS1 knockdown suppressed NLRP3 inflammasome activity via promoting autophagy and then attenuated sepsis-induced acute lung injury, revealing a novel target for treating sepsis-induced lung injury.

GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome

Objective

A hitherto undescribed phenotype of early onset muscular dystrophy associated with sensorineural hearing loss and primary ovarian insufficiency was initially identified in 2 siblings and in subsequent patients with a similar constellation of findings. The goal of this study was to understand the genetic and molecular etiology of this condition.

Methods

We applied whole exome sequencing (WES) superimposed on shared haplotype regions to identify the initial biallelic variants in GGPS1 followed by GGPS1 Sanger sequencing or WES in 5 additional families with the same phenotype. Molecular modeling, biochemical analysis, laser membrane injury assay, and the generation of a Y259C knock‐in mouse were done.

Results

A total of 11 patients in 6 families carrying 5 different biallelic pathogenic variants in specific domains of GGPS1 were identified. GGPS1 encodes geranylgeranyl diphosphate synthase in the mevalonate/isoprenoid pathway, which catalyzes the synthesis of geranylgeranyl pyrophosphate, the lipid precursor of geranylgeranylated proteins including small guanosine triphosphatases. In addition to proximal weakness, all but one patient presented with congenital sensorineural hearing loss, and all postpubertal females had primary ovarian insufficiency. Muscle histology was dystrophic, with ultrastructural evidence of autophagic material and large mitochondria in the most severe cases. There was delayed membrane healing after laser injury in patient‐derived myogenic cells, and a knock‐in mouse of one of the mutations (Y259C) resulted in prenatal lethality.

Interpretation

The identification of specific GGPS1 mutations defines the cause of a unique form of muscular dystrophy with hearing loss and ovarian insufficiency and points to a novel pathway for this clinical constellation. ANN NEUROL 2020;88:332–347.

Geranylgeranyl diphosphate synthase deficiency aggravates lung fibrosis in mice by modulating TGF-β1/BMP-4 signaling

Geranylgeranyl diphosphate synthase (GGPPS) is an enzyme that catalyzes the synthesis of geranylgeranyl pyrophosphate (GGPP). GGPPS is implicated in many disorders, but its role in idiopathic pulmonary fibrosis (IPF) remains unclear. This study aimed to investigate the role of GGPPS in IPF. We established bleomycin-induced lung injury in a lung-specific GGPPS-deficient mouse (GGPPS-/-) and detected GGPPS expression in lung tissues by Western blot and immunohistochemistry analysis. We found that GGPPS expression increased during lung injury and fibrosis in mice induced by bleomycin, and GGPPS deficiency augmented lung fibrosis. GGPPS deficiency activated lung fibroblast by facilitating transforming growth factor β1 while antagonizing bone morphogenetic protein 4 signaling. Notably, the supplementation of exogenous GGPP mitigated lung fibrosis in GGPPS-/- mice induced by bleomycin. In conclusion, our findings suggest that GGPPS provides protection against pulmonary fibrosis and that the restoration of protein geranylgeranylation may benefit statin-induced lung injury.

Geranylgeranyl diphosphate synthase 1 knockout ameliorates ventilator-induced lung injury via regulation of TLR2/4-AP-1 signaling

OBJECTIVE

To investigate the role of geranylgeranyl diphosphate synthase 1 (GGPPS1) in ventilator-induced lung injury along with the underlying mechanism.

METHODS

A murine VILI model was induced by high-tidal volume ventilation in both wild-type and GGPPS1 knockout mice. GGPPS1 expression was detected in the bronchoalveolar lavage fluid (BALF) supernatants of acute respiratory distress syndrome (ARDS) patients and healthy volunteers, as well as in lung tissues and BALF supernatants of the VILI mice using enzyme-linked immunosorbent assay (ELISA), quantitative reverse transcription polymerase chain reaction (qRT-PCR), western bolt and immunohistochemical (IHC). The wet/dry ratio, total BALF proteins, and lung injury score were analyzed. The percentage of neutrophils was detected by flow cytometry and IHC. Inflammatory cytokine levels were measured by ELISA and qRT-PCR. The related expression of Toll-like receptor (TLR)2/4 and its downstream proteins was evaluated by western blot.

RESULTS

GGPPS1 in BALF supernatants was upregulated in ARDS patients and the VILI mice. Depletion of GGPPS1 significantly alleviated the severity of ventilator induced lung injury in mice. Total cell count, neutrophils and inflammatory cytokines (interleukin [IL]-6, IL-1β, IL-18 and tumor necrosis factor-α) levels in BALF were reduced after GGPPS1 depletion. Moreover, addition of exogenous GGPP in GGPPS-deficient mice significantly exacerbated the severity of ventilator induced lung injury as compared to the PBS treated controls. Mechanistically, the expression of TLR2/4, as well as downstream proteins including activator protein-1 (AP-1) was suppressed in lung tissues of GGPPS1-deficient mice.

CONCLUSION

GGPPS1 promoted the pathogenesis of VILI by modulating the TLR2/4-AP-1 signaling pathway, and GGPPS1 knockout significantly alleviated the lung injury and inflammation in the VILI mice.

Conditional loss of geranylgeranyl diphosphate synthase alleviates acute obstructive cholestatic liver injury by regulating hepatic bile acid metabolism

Previous studies have suggested that metabolites in the mevalonate pathway are involved in hepatic bile acid metabolism, yet the details of this relationship remain unknown. In this study, we found that the hepatic farnesyl pyrophosphate (FPP) level and the ratio of FPP to geranylgeranyl pyrophosphate (GGPP) were increased in mice with acute obstructive cholestasis compared with mice that underwent a sham operation. In addition, the livers of the mice with acute obstructive cholestasis showed lower expression of geranylgeranyl diphosphate synthase (GGPPS), which synthesizes GGPP from FPP. When Ggps1 was conditionally deleted in the liver, amelioration of liver injury, as shown by downregulation of the hepatic inflammatory response and decreased hepatocellular apoptosis, was found after ligation of the common bile duct and cholecystectomy (BDLC). Subsequently, liquid chromatography/mass spectrometry analysis showed that knocking out Ggps1 decreased the levels of hepatic bile acids, including hydrophobic bile acids. Mechanistically, the disruption of Ggps1 increased the levels of hepatic FPP and its metabolite farnesol, thereby resulting in farnesoid X receptor (FXR) activation, which modulated hepatic bile acid metabolism and reduced hepatic bile acids. It was consistently indicated that digeranyl bisphosphonate, a specific inhibitor of GGPPS, and GW4064, an agonist of FXR, could also alleviate acute obstructive cholestatic liver injury in vivo. In general, GGPPS is critical for modulating acute obstructive cholestatic liver injury, and the inhibition of GGPPS ameliorates acute obstructive cholestatic liver injury by decreasing hepatic bile acids, which is possibly achieved through the activation of FXR-induced bile acid metabolism.

Inhibition of GGPPS1 attenuated LPS-induced acute lung injury and was associated with NLRP3 inflammasome suppression

Inhibition of the mevalonate pathway using statins has been shown to be beneficial in the treatment of acute lung injury (ALI). Here, we investigated whether partial inhibition of this pathway by targeting geranylgeranyl pyrophosphate synthase large subunit 1 (GGPPS1), a catalase downstream of the mevalonate pathway, was effective at treating lung inflammation in ALI. Lipopolysaccharide (LPS) was intratracheally instilled to induce ALI in lung-specific GGPPS1-knockout and wild-type mice. Expression of GGPPS1 in lung tissues and alveolar epithelial cells was examined. The severity of lung injury and inflammation was determined in lung-specific GGPPS1 knockout and wild-type mice by measuring alveolar exudate, neutrophil infiltration, lung injury, and cell death. Change in global gene expression in response to GGPPS1 depletion was measured using mRNA microarray and verified in vivo and in vitro. We found that GGPPS1 levels increased significantly in lung tissues and alveolar epithelial cells in LPS-induced ALI mice. Compared with wild-type and simvastatin treated mice, the specific deletion of pulmonary GGPPS1 attenuated the severity of lung injury by inhibiting apoptosis of AECs. Furthermore, deletion of GGPPS1 inhibited LPS-induced inflammasome activation, in terms of IL-1β release and pyroptosis, by downregulating NLRP3 expression. Finally, downregulation of GGPPS1 reduced the membrane expression of Ras-related protein Rab10 and Toll-like receptor 4 (TLR4) and inhibited the phosphonation of IκB. This effect might be attributed to the downregulation of GGPP levels. Our results suggested that inhibition of pulmonary GGPPS1 attenuated LPS-induced ALI predominantly by suppressing the NLRP3 inflammasome through Rab10-mediated TLR4 replenishment.

Reduced triglyceride accumulation due to overactivation of farnesoid X receptor signaling contributes to impaired liver regeneration following 50% hepatectomy in extra‑cholestatic liver tissue

The aim of the present study was to investigate the role of triglyceride metabolism in the effect of obstructive cholestasis on liver regeneration following 50% partial hepatectomy (PH). Obstructive cholestatic rat models were achieved via ligation of the common bile duct (BDL). Following comparisons between hepatic pathological alterations with patients with perihilar cholangiocarcinoma, rats in the 7 day post‑BDL group were selected as the BDL model for subsequent experiments. Liver weight restoration, proliferating cell nuclear antigen labeling index, cytokine and growth factor expression levels, and hepatic triglyceride content were evaluated to analyze liver regeneration post‑PH within BDL and control group rats. The results of the present study revealed that obstructive cholestasis impaired liver mass restoration, which occurred via inhibition of early stage hepatocyte proliferation. In addition, reduced triglyceride content and inhibited expression of fatty acid β‑oxidation‑associated genes, peroxisome proliferator activated receptor α and carnitine palmitoyltransferase, were associated with an insufficient energy supply within the BDL group post‑PH. Notably, the expression levels of fatty acid synthesis‑associated genes, including sterol‑regulatory element‑binding protein‑1c, acetyl‑coA carboxylase 1 and fatty acid synthase were also reduced within the BDL group, which accounted for the reduced triglyceride content and fatty acid utilization. Further investigation revealed that overactivated farnesoid X receptor (FXR) signaling may inhibit fatty acid synthesis within BDL group rats. Collectively, the role of triglycerides in liver regeneration following PH in extra‑cholestatic livers was identified in the present study. Additionally, the results indicated that overactivated FXR signaling‑induced triglyceride reduction is associated with insufficient energy supply and therefore contributes to the extent of impairment of liver regeneration following PH within extra‑cholestatic livers.