GDI2 deletion alleviates neurodegeneration and memory loss in the 5xFAD mice model of Alzheimer's disease.

Accumulation of insoluble deposits of amyloid ß-peptide (Aß), derived from amyloid precursor protein (APP) processing, represents one of the major pathological hallmarks of Alzheimer's disease (AD). Perturbations in APP transport and hydrolysis could lead to increased Aß production. However, the precise mechanisms underlying APP transport remain elusive. The GDP dissociation inhibitor2 (GDI2), a crucial regulator of Rab GTPase activity and intracellular vesicle and membrane trafficking, was investigated for its impact on AD pathogenesis through neuron-specific knockout of GDI2 in 5xFAD mice. Notably, deficiency of GDI2 significantly ameliorated cognitive impairment, prevented neuronal loss in the subiculum and cortical layer V, reduced senile plaques as well as astrocyte activation in 5xFAD mice. Conversely, increased activated microglia and phagocytosis were observed in GDI2 ko mice. Further investigation revealed that GDI2 knockout led to more APP co-localized with the ER rather than the Golgi apparatus and endosomes in SH-SY5Y cells, resulting in decreased Aß production. Collectively, these findings suggest that GDI2 may regulate Aß production by modulating APP intracellular transport and localization dynamics. In summary, our study identifies GDI2 as a pivotal regulator governing APP transport and process implicated in AD pathology; thus highlighting its potential as an attractive pharmacological target for future drug development against AD.

Exploring the impact of CYP2D6 and UGT2B7 gene-drug interactions, and CYP-mediated DDI on oxycodone and oxymorphone pharmacokinetics using physiologically-based pharmacokinetic modeling and simulation.

Oxycodone is one of the most commonly used opioids to treat moderate to severe pain. It is metabolized mainly by CYP3A4 and CYP2D6, while only a small fraction of the dose is excreted unchanged into the urine. Oxymorphone, the metabolite primarily formed by CYP2D6, has a 40- to 60-fold higher mu-opioid receptor affinity than the parent compound. While CYP2D6-mediated gene-drug-interactions (GDIs) and drug-drug interactions (DDIs) are well-studied, they only account for a portion of the variability in oxycodone and oxymorphone exposure. The combined impact of CYP2D6-mediated GDIs and DDIs, CYP3A4-mediated DDIs, and UGT2B7 GDIs is not fully understood yet and hard to study in head-to-head clinical trials given the relatively large number of scenarios. Instead, we propose the use of a physiologically-based pharmacokinetic model that integrates available information on oxycodone's metabolism to characterize and predict the impact of DDIs and GDIs on the exposure of oxycodone and its major, pharmacologically-active metabolite oxymorphone. To this end, we first developed and verified a PBPK model for oxycodone and its metabolites using published clinical data. The verified model was then applied to determine the dose-exposure relationship of oxycodone and oxymorphone stratified by CYP2D6 and UGT2B7 phenotypes respectively, and administered perpetrators of CYP-based drug interactions. Our simulations demonstrate that the combination of CYP2D6 UM and a UGT2B7Y (268) mutation may lead to a 2.3-fold increase in oxymorphone exposure compared to individuals who are phenotyped as CYP2D6 NM / UGT2B7 NM. The extent of oxymorphone exposure increases up to 3.2-fold in individuals concurrently taking CYP3A4 inhibitors, such as ketoconazole. Inhibition of the CYP3A4 pathway results in a relative increase in the partial metabolic clearance of oxycodone to oxymorphone. Oxymorphone is impacted to a higher extent by GDIs and DDIs than oxycodone. We predict oxymorphone exposure to be highest in CYP2D6 UMs/UGT2B7 PMs in the presence of ketoconazole (strong CYP3A4 index inhibitor) and lowest in CYP2D6 PMs/UGT2B7 NMs in the presence of rifampicin (strong CYP3A4 index inducer) covering a 55-fold exposure range.

ECM1-associated miR-1260b promotes osteogenic differentiation by targeting GDI1.

Osteoporosis (OP) is a common disease among older adults. The promotion of osteoblast differentiation plays a crucial role in alleviating OP symptoms. Extracellular matrix protein 1 (ECM1) has been reported to be closely associated with osteogenic differentiation. In this study, we constructed U2OS cell lines with ECM1 knockdown and ECM1a overexpression based on knockdown, and identified the target miRNA (miR-1260b) by sequencing. Overexpression of miR-1260b promoted the osteogenic differentiation of U2OS and MG63 cells, as demonstrated by increased alkaline phosphatase (ALP) activity, matrix mineralization, and Runt-Related Transcription Factor 2 (RUNX2), Osteopontin (OPN), Collagen I (COL1A1), and Osteocalcin (OCN) protein expressions, whereas low expression of miR-1260b had the opposite effect. In addition, miR-1260b expression was decreased in OP patients than in non-OP patients. Next, we predicted the target gene of miRNA through TargetScan and miRDB and found that miR-1260b negatively regulated GDP dissociation inhibitor 1 (GDI1) by directly binding to its 3'-untranslated region. Subsequent experiments revealed that GDI1 overexpression decreased ALP activity and calcium deposit, reduced RUNX2, OPN, COL1A1, and OCN expression levels, and reversed the effects of miR-1260b on osteogenic differentiation. In conclusion, ECM1-related miR-1260b promotes osteogenic differentiation by targeting GDI1 in U2OS and MG63 cells. Thus, this study has significant implication for osteoporosis treatment.

Effect of different ceramic systems on antagonist dental structure by microtomographic analysis.

OBJECTIVES: This study aims to identify the two-dimensional and three-dimensional analyses and evaluate the loss of tooth structure in the tooth's different constituent elements and the ceramic antagonist's surface. METHODS: In this study, three groups (n = 10) represented by different ceramic systems (lithium disilicate [GDis], lithium silicate reinforced with zirconia [GSil], and monolithic zirconia [GZir]) were evaluated. Each group obtained ten ceramic blocks and submitted them to the sintering/crystallization process. To carry out the wear test, healthy mandibular premolars were used as the specimens and the ceramic blocks as antagonists. The premolars were submitted to two-dimensional and three-dimensional analyses using a computerized microtomography (µTC) before and after the wear test. The wear test was performed with 30 N and 300,000 cycles load, with occlusion, laterality, and disocclusion movements. RESULTS: The statistical analysis comparing the loss of two-dimensional tooth structure showed a statistically significant difference among all groups (p < 0.05). Statistical analysis comparing the percentage of loss of three-dimensional tooth structure showed a statistically significant difference between groups GDis and GSil and between groups GDis and GZir. However, when comparing GSil with GZir, no statistically significant difference was found. The qualitative analysis of the teeth showed that GDis showed considerable enamel loss and dentin exposure, GSil showed enamel wear with flattening the cusp without dentin exposure, and GZir showed minimal enamel wear without dentin exposure. In the qualitative analysis of ceramic antagonists, more significant wear of the ceramic material for GDis was observed, followed by the GSil and GZir groups, respectively. SIGNIFICANCE: The use of the lithium disilicate should be cautious, restricting it to areas with lower masticatory forces. Areas of higher masticatory forces showed a large amount of antagonist wear, with dentin involvement. This can lead to dentinal hypersensitivity, risk of compromising patients' occlusion, by harming group disocclusion guides, causing pain and temporomandibular disorders.

Molecular mechanism of regulation of RhoA GTPase by phosphorylation of RhoGDI.

Rho-specific guanine nucleotide dissociation inhibitors (RhoGDIs) play a crucial role in the regulation of Rho family GTPases. They act as negative regulators that prevent the activation of Rho GTPases by forming complexes with the inactive GDP-bound state of GTPase. Release of Rho GTPase from the RhoGDI-bound complex is necessary for Rho GTPase activation. Biochemical studies provide evidence of a "phosphorylation code," where phosphorylation of some specific residues of RhoGDI selectively releases its GTPase partner (RhoA, Rac1, Cdc42, etc.). This work attempts to understand the molecular mechanism behind this specific phosphorylation-induced reduction in binding affinity. Using several microseconds long atomistic molecular dynamics simulations of the wild-type and phosphorylated states of the RhoA-RhoGDI complex, we propose a molecular-interaction-based mechanistic model for the dissociation of the complex. Phosphorylation induces major structural changes, particularly in the positively charged polybasic region (PBR) of RhoA and the negatively charged N-terminal region of RhoGDI that contribute most to the binding affinity. Molecular mechanics Poisson-Boltzmann surface area binding energy calculations show a significant weakening of interaction on phosphorylation at the RhoA-specific site of RhoGDI. In contrast, phosphorylation at a Rac1-specific site does not affect the overall binding affinity significantly, which confirms the presence of a phosphorylation code. RhoA-specific phosphorylation leads to a reduction in the number of contacts between the PBR of RhoA and the N-terminal region of RhoGDI, which manifests a reduction of the binding affinity. Using hydrogen bond occupancy analysis and energetic perturbation network, we propose a mechanistic model for the allosteric response, i.e., long-range signal propagation from the site of phosphorylation to the PBR and buried geranylgeranyl group in the form of rearrangement and rewiring of hydrogen bonds and salt bridges. Our results highlight the crucial role of specific electrostatic interactions in manifestation of the phosphorylation code.

GDP dissociation inhibitor 1 (GDI1) attenuates ß-amyloid-induced neurotoxicity in Alzheimer's diseases.

OBJECTIVE: ß-Amyloid (Aß) induced neurotoxicity is an implicated mechanism in Alzheimer's disease (AD). This study focused on the role of GDP dissociation inhibitor 1 (GDI1) in Aß-induced neurotoxicity. METHODS: Data from the GEO database for AD-related datasets GSE140829, GSE63061, GSE36980, and GSE60360 were downloaded and identified common differentially expressed genes (coDEGs). The mRNA levels of GDI1 in the serum of AD patients were analyzed by RT-qPCR. ROC curve evaluated the diagnostic value. Aß25-35 induced SH-SY5Y cells to construct an AD cell model. CCK-8, flow cytometry, and ELISA assay were used to analyze cell viability, apoptosis, and concentrations of inflammatory factors. KEGG enrichment was employed to analyze the signal pathway of targets from GDI1 in the AD. RESULTS: The GEO database identifies coDEGs including GDI1. GDI1 is generally elevated in serum from AD patients as well as in Aß-induced SH-SY5Y cells. GDI1 has 77.97% sensitivity and 84.44% specificity to identify AD patients from controls. Aß induced decreased cell viability, increased apoptosis, and promoted over-secretion of inflammatory cytokines, but they were all partially weakened by reduced GDI1. What's more, the GDI1 interacting gene and AD target gene were co-enriched on Endocytosis and MAPK signaling pathway. CONCLUSION: Elevated GDI1 is a potential diagnostic biomarker for AD and that inhibition of GDI1 attenuates Aß-induced neurotoxicity in AD. Our study offers new horizons for AD treatment.

The effects of the first versus second glaucoma drainage implant surgery in patients with primary open-angle glaucoma.

BACKGROUND: To investigate the outcome of non-valved glaucoma drainage implant surgery (GDIS) in primary open-angle glaucoma (POAG) patients divided in the first GDI group (patients who underwent the first GDIS) and the second GDI group (patients who underwent the second GDIS because of the failed first GDIS). METHODS: Intraocular pressure (IOP), visual acuity (VA), visual field defect (VFD), medication score (MS), survival rate of GDIS, complications, and patient background was retrospectively analyzed. Two success criteria were set: Criteria (1) IOP reduction ≥ 20% and 5 < IOP ≤ 21, Criteria (2) IOP reduction ≥ 20% and 5 < IOP ≤ 14. RESULTS: There were 136 eyes of 109 patients in the first GDI group and 32 eyes of 27 patients in the second GDI group. In the first GDI group and II, mean preoperative IOP was 26.7 ± 6.7 mmHg and 23.7 ± 3.5 mmHg, respectively (P = 0.09). No statistically significant difference in postoperative IOP reduction was found between the two groups (P = 0.39). At 5-years postoperative, the Criteria 1 (Criteria 2) survival rate in the first GDI group and the second GDI group was 60.4% (31.7%) and 61.2% (25.6%), respectively (Criteria 1: hazard ratio [HR]: 0.64, 95% confidence interval [CI]: 0.30-1.35 [P = 0.24]; Criteria 2: HR: 0.81, 95% CI: 0.46-1.44, P = 0.48). No significant difference in VA, VFD change, MS, or complications was observed. Young patient age was the only significant factor for failure in the first GDI group (odds ratio: 0.95, 95% confidence interval: 0.91-1.00, P = 0.03). CONCLUSION: The second GDIS may be as effective as the first GDIS for IOP reduction in POAG patients, however, there is a high risk of failure in young-age patients and the surgery may be ineffective in eyes requiring Criteria 2.

Implementation of pharmacogenetic testing in medication reviews in a hospital setting.

AIM: To investigate whether it is feasible to perform pharmacogenetic testing and implement the test results as part of medication reviews during hospitalization of multimorbid patients. METHODS: Patients with ≥2 chronic conditions and ≥5 regular drugs with at least one potential gene-drug interaction (GDI) were included from one geriatric and one cardiology ward for pharmacogenetic testing. After inclusion by the study pharmacist, blood samples were collected and shipped to the laboratory for analysis. For patients still hospitalized at the time when the pharmacogenetic test results were available, the information was used in medication reviews. Recommendations from the pharmacist on actionable GDIs were communicated to the hospital physicians, who subsequently decided on potential immediate changes or forwarded suggestions in referrals to general practitioners. RESULTS: The pharmacogenetic test results were available for medication review in 18 of the 46 patients (39.1%), where median length of hospital stay was 4.7 days (1.6-18.3). The pharmacist recommended medication changes for 21 of 49 detected GDIs (42.9%). The hospital physicians accepted 19 (90.5%) of the recommendations. The most commonly detected GDIs involved metoprolol (CYP2D6 genotype), clopidogrel (CYP2C19 genotype) and atorvastatin (CYP3A4/5 and SLCOB1B1 genotype). CONCLUSIONS: The study shows that implementation of pharmacogenetic testing for medication review of hospitalized patients has the potential to improve drug treatment before being transferred to primary care. However, the logistics workflow needs to be further optimized, as test results were available during hospitalization for less than half of the patients included in the study.

Investigating Gene-Diet Interactions Impacting the Association Between Macronutrient Intake and Glycemic Traits.

Few studies have demonstrated reproducible gene-diet interactions (GDIs) impacting metabolic disease risk factors, likely due in part to measurement error in dietary intake estimation and insufficient capture of rare genetic variation. We aimed to identify GDIs across the genetic frequency spectrum impacting the macronutrient-glycemia relationship in genetically and culturally diverse cohorts. We analyzed 33,187 participants free of diabetes from 10 National Heart, Lung, and Blood Institute Trans-Omics for Precision Medicine program cohorts with whole-genome sequencing, self-reported diet, and glycemic trait data. We fit cohort-specific, multivariable-adjusted linear mixed models for the effect of diet, modeled as an isocaloric substitution of carbohydrate for fat, and its interactions with common and rare variants genome-wide. In main effect meta-analyses, participants consuming more carbohydrate had modestly lower glycemic trait values (e.g., for glycated hemoglobin [HbA1c], -0.013% HbA1c/250 kcal substitution). In GDI meta-analyses, a common African ancestry-enriched variant (rs79762542) reached study-wide significance and replicated in the UK Biobank cohort, indicating a negative carbohydrate-HbA1c association among major allele homozygotes only. Simulations revealed that >150,000 samples may be necessary to identify similar macronutrient GDIs under realistic assumptions about effect size and measurement error. These results generate hypotheses for further exploration of modifiable metabolic disease risk in additional cohorts with African ancestry. ARTICLE HIGHLIGHTS: We aimed to identify genetic modifiers of the dietary macronutrient-glycemia relationship using whole-genome sequence data from 10 Trans-Omics for Precision Medicine program cohorts. Substitution models indicated a modest reduction in glycemia associated with an increase in dietary carbohydrate at the expense of fat. Genome-wide interaction analysis identified one African ancestry-enriched variant near the FRAS1 gene that may interact with macronutrient intake to influence hemoglobin A1c. Simulation-based power calculations accounting for measurement error suggested that substantially larger sample sizes may be necessary to discover further gene-macronutrient interactions.

RhoA regulation in space and time.

RhoGTPases are well known for being controllers of cell cytoskeleton and share common features in the way they act and are controlled. These include their switch from GDP to GTP states, their regulations by different guanine exchange factors (GEFs), GTPase-activating proteins and guanosine dissociation inhibitors (GDIs), and their similar structure of active sites/membrane anchors. These very similar features often lead to the common consideration that the differences in their biological effects mainly arise from the different types of regulators and specific effectors associated with each GTPase. Focusing on data obtained through biosensors, live cell microscopy and recent optogenetic approaches, we highlight in this review that the regulation of RhoA appears to depart from Cdc42 and Rac1 modes of regulation through its enhanced lability at the plasma membrane. RhoA presents a high dynamic turnover at the membrane that is regulated not only by GDIs but also by GEFs, effectors and a possible soluble conformational state. This peculiarity of RhoA regulation may be important for the specificities of its functions, such as the existence of activity waves or its putative dual role in the initiation of protrusions and contractions.

GPSM1 impairs metabolic homeostasis by controlling a pro-inflammatory pathway in macrophages.

G-protein-signaling modulator 1 (GPSM1) exhibits strong genetic association with Type 2 diabetes (T2D) and Body Mass Index in population studies. However, how GPSM1 carries out such control and in which types of cells are poorly understood. Here, we demonstrate that myeloid GPSM1 promotes metabolic inflammation to accelerate T2D and obesity development. Mice with myeloid-specific GPSM1 ablation are protected against high fat diet-induced insulin resistance, glucose dysregulation, and liver steatosis via repression of adipose tissue pro-inflammatory states. Mechanistically, GPSM1 deficiency mainly promotes TNFAIP3 transcription via the Gαi3/cAMP/PKA/CREB axis, thus inhibiting TLR4-induced NF-κB signaling in macrophages. In addition, we identify a small-molecule compound, AN-465/42243987, which suppresses the pro-inflammatory phenotype by inhibiting GPSM1 function, which could make it a candidate for metabolic therapy. Furthermore, GPSM1 expression is upregulated in visceral fat of individuals with obesity and is correlated with clinical metabolic traits. Overall, our findings identify macrophage GPSM1 as a link between metabolic inflammation and systemic homeostasis.

The atypical Rab GTPase associated with Parkinson's disease, Rab29, is localized to membranes.

Several genetic studies have shown that the small GTPase Rab29 is involved in the pathogenesis of Parkinson's Disease (PD). It has also been shown that overexpression of Rab29 increases the activity of leucine-rich repeat kinase 2, a protein kinase often mutated in familial PD, although the mechanism underlying this activation remains unclear. Here, we employed biochemical analyses to characterize the localization of Rab29 and found that, unlike general Rab proteins, Rab29 is predominantly fractionated into the membrane fraction by ultracentrifugation. We also found that Rab29 is resistant to extraction from membranes by GDP-dissociation inhibitors (GDIs) in vitro. Furthermore, Rab29 failed to interact with GDIs, and its membrane localization was not affected by the knockout of GDIs in cells. We show that the knockout of Rab geranylgeranyltransferase decreased the hydrophobicity of Rab29, suggesting that Rab29 is geranylgeranylated at its carboxyl terminus as is with typical Rab proteins. Notably, we demonstrated that membrane-bound Rab29 retains some hydrophilicity, indicating that mechanisms other than geranylgeranylation might also be involved in the membrane localization of Rab29. Taken together, these findings uncover the atypical nature of Rab29 among Rab proteins, which will provide important clues for understanding how Rab29 is involved in the molecular pathomechanism of PD.

Targeted disruption of Gdi2 causes early embryonic lethality.

INTRODUCTION: GDI2 regulates the GDP/GTP exchange reaction of Rab proteins by inhibiting the dissociation of GDP and the subsequent binding of GTP, dysregulation of GDI2 has been reported in many different cancers. Recently, we found that GDI2 bound to the ITIM domain of Siglec-G under normal homeostasis, whereas Rab1a was recruited to the ITIM domain during bacterial infection. Therefore, GDI2 and Rab1a may regulate the immune response through interaction with the ITIM domain during bacterial infection. However, the regulation of the inflammatory response by GDI2 in vivo and its regulatory mechanism remain unknown. METHODS: We generated a Gdi2 null mutant mouse with a trapped Gdi2 gene and examined the expression by X-gal and immunohistochemistry staining. TUNEL staining was used to determine the apoptosis cells. RESULTS: Here we show that Gdi2 is essential for embryonic development. One functional Gdi2 allele is sufficient for murine embryo development, but complete loss of Gdi2 leads to embryonic lethality. Developmental retardation of Gdi2-/- mice is apparent at E10.5 to E14.5, with no viable Gdi2-/- embryos detected after E14.5. Histological analysis revealed extensive cell death and cell loss in Gdi2-/- embryos. Apoptosis was confirmed by staining with cleaved caspase-3, suggesting that Gdi2 maintain homeostasis by regulating the apoptosis of the cells. There was no significant difference in cytokine production and survival between wild-type and Gdi2+/- mice after LPS challenge. DISCUSSION: These findings suggest that one Gdi2 allele is sufficient to maintain function. However, the detailed molecular mechanism underlying Gdi2 in regulating the embryonic development needs further identification.

GDI2 is a novel diagnostic and prognostic biomarker in hepatocellular carcinoma.

BACKGROUND: GDP Dissociation inhibitor 2 (GDI2) gene has been correlated with some important biological processes in a variety of cancers, whereas the role of GDI2 in hepatocellular carcinoma (HCC) is ill-defined. We aimed to demonstrate the relationship between GDI2 and HCC based on The Cancer Genome Atlas (TCGA) data mining. METHODS: The expression of GDI2 was compared between cancer and normal tissues of 371 HCC patients collected from TCGA-LIHC, and verified in HCC cell lines. Gene set enrichment analysis (GSEA) was applied to annotate biological function of GDI2. Furthermore, Wilcoxon rank sum test, Logistics regression, as well as Cox regression and Kaplan-Meier survival analysis, were employed to evaluate the association of GDI2 expression with clinicopathological characteristics, and survival status of HCC patients, respectively. RESULTS: It showed that the expression of GDI2 was much higher in tumor tissues than in normal tissues (P < 0.001) of HCC patients. And the elevated expression of GDI2 was correlated with more aggressive HCC tumor status, including severe primary tumor extent, advanced pathological stage, serious histologic grade, and mutated TP53 status (P < 0.05). Moreover, high GDI2 expression was strongly associated with a poor survival rate (P < 0.001). Both enrichment and immune infiltration analyses implied that GDI2-associated signaling mainly involve lipid metabolism and extracellular matrix (ECM) constructing pathways related to tumor microenvironment (TME) (P < 0.05). CONCLUSIONS: The elevated expression of GDI2 predicts poor prognosis in HCC patients, indicating that GDI2 could be applied as a predictive biomarker for diagnosis and prognosis of HCC.

Electrostatic Forces Mediate the Specificity of RHO GTPase-GDI Interactions.

Three decades of research have documented the spatiotemporal dynamics of RHO family GTPase membrane extraction regulated by guanine nucleotide dissociation inhibitors (GDIs), but the interplay of the kinetic mechanism and structural specificity of these interactions is as yet unresolved. To address this, we reconstituted the GDI-controlled spatial segregation of geranylgeranylated RHO protein RAC1 in vitro. Various biochemical and biophysical measurements provided unprecedented mechanistic details for GDI function with respect to RHO protein dynamics. We determined that membrane extraction of RHO GTPases by GDI occurs via a 3-step mechanism: (1) GDI non-specifically associates with the switch regions of the RHO GTPases; (2) an electrostatic switch determines the interaction specificity between the C-terminal polybasic region of RHO GTPases and two distinct negatively-charged clusters of GDI1; (3) a non-specific displacement of geranylgeranyl moiety from the membrane sequesters it into a hydrophobic cleft, effectively shielding it from the aqueous milieu. This study substantially extends the model for the mechanism of GDI-regulated RHO GTPase extraction from the membrane, and could have implications for clinical studies and drug development.

Overexpression of GDP dissociation inhibitor 1 gene associates with the invasiveness and poor outcomes of colorectal cancer.

GDP dissociation inhibitor (GDI) regulates the GDP/GTP exchange reaction of most Rab proteins by inhibiting GDP dissociation. This study evaluated the potential prognostic and predictive value of GDI1 in colorectal cancer (CRC). To address the prognostic power of GDI1, we performed individual and pooled survival analyses on six independent CRC microarray gene expression datasets. GDI1-enriched signatures were also analyzed. Kaplan-Meier and Cox proportional analyses were employed for survival analysis. An immunohistochemistry (IHC) analysis was performed to validate the clinical relevance and prognostic significance of the GDI1 protein level in CRC tissue samples. The results revealed that GDI1 mRNA level was significantly linked with the aggressiveness of CRC, which is compatible with gene set enrichment analysis. A meta-analysis and pooled analysis demonstrated that a higher mRNA GDI1 expression was dramatically correlated with a worse survival in a dose-dependent manner in CRC patients. Further IHC analysis validated that the protein expression of GDI1 in both cytoplasm and membrane also significantly impacted the outcome of CRC patients. In CRC patients with stage III, chemotherapy significantly reduced the relative risk of death in low-GDI1 subgroup (hazard ratio (HR) = 0.22; 95% confidence interval (95% CI) 0.09-0.56, p = 0.0003), but not in high-GDI1 subgroup (HR = 0.63; 95% CI 0.35-1.14, p = 0.1137). Therefore, both high mRNA and protein levels of GDI1 were significantly related to poor outcomes in CRC patients. GD11 may serve as a prognostic biomarker for CRC.

ISGylation drives basal breast tumour progression by promoting EGFR recycling and Akt signalling.

ISG15 is an ubiquitin-like modifier that is associated with reduced survival rates in breast cancer patients. The mechanism by which ISG15 achieves this however remains elusive. We demonstrate that modification of Rab GDP-Dissociation Inhibitor Beta (GDI2) by ISG15 (ISGylation) alters endocytic recycling of the EGF receptor (EGFR) in non-interferon stimulated cells using CRISPR-knock out models for ISGylation. By regulating EGFR trafficking, ISGylation enhances EGFR recycling and sustains Akt-signalling. We further show that Akt signalling positively correlates with levels of ISG15 and its E2-ligase in basal breast cancer cohorts, confirming the link between ISGylation and Akt signalling in human tumours. Persistent and enhanced Akt activation explains the more aggressive tumour behaviour observed in human breast cancers. We show that ISGylation can act as a driver of tumour progression rather than merely being a bystander.

Imaging of Spatial Cycling of Rab GTPase in the Cell.

Rab GTPases (>60 members in human) function as master regulators of intracellular membrane trafficking. To fulfill their functions, Rab proteins need to localize on specific membranes in cells. It remains elusive how the distinct spatial distribution of Rab GTPases in the cell is regulated. To make a global assessment on the subcellular localization of Rab1, we determined kinetic parameters of the spatial cycling of Rab1 in live cells using photoactivatable fluorescent proteins and live cell imaging. We found that the switching between GTP- and GDP-binding states, which is governed by guanine nucleotide exchange factors (GEFs), GTPase activating proteins (GAPs), GDP dissociation inhibitor (GDI) and GDI displacement factor (GDF), is a major determinant for Rab1's ability to effectively cycle between cellular compartments and eventually for its subcellular distribution. Herein, we describe the method for monitoring Rab1 dynamics in live cells. This approach can be used to study spatial cycling of other Rab GTPases.

Knockdown of GPSM1 Inhibits the Proliferation and Promotes the Apoptosis of B-Cell Acute Lymphoblastic Leukemia Cells by Suppressing the ADCY6-RAPGEF3-JNK Signaling Pathway.

B-cell acute lymphoblastic leukemia (B-ALL) is the common type of blood cancer. Although the remission rate has increased, the current treatment options for B-ALL are usually related to adverse reactions and recurrence, so it is necessary to find other treatment options. G protein signaling modulator 1 (GPSM1) is one of several factors that affect the basic activity of the G protein signaling system, but its role in B-ALL has not yet been clarified. In this study, we analyzed the expression of GPSM1 in the Oncomine database and found that the GPSM1 levels were higher in B-ALL cells than in peripheral blood mononuclear cells (PBMCs). Analyses of the Gene Expression Profiling Interactive Analysis (GEPIA) demonstrated that patients with high GPSM1 levels had shorter survival times than those with low levels. Additionally, gene set enrichment analysis (GSEA) suggested that GPSM1 was positively correlated with proliferation, G protein-coupled receptor (GPCR) ligand binding, Gαs signaling and calcium signaling pathways. In further experiments, GPSM1 was found to be highly expressed in Acute lymphoblastic leukemia (ALL) cell lines, and downregulation of GPSM1 inhibited proliferation and promoted cell cycle arrest and apoptosis in BALL-1 and Reh cells. Moreover, knockdown of GPSM1 suppressed ADCY6 and RAPGEF3 expression in BALL-1 and Reh cells. Furthermore, we reported that GPSM1 regulated JNK expression via ADCY6-RAPGEF3. The present study demonstrates that GPSM1 promotes tumor growth in BALL-1 and Reh cells by modulating ADCY6-RAPGEF3-JNK signaling.

GDI2 is a target of paclitaxel that affects tumorigenesis of prostate cancer via the p75NTR signaling pathway.

BACKGROUND: Prostate cancer (PCa) refers to malignant tumors derived from prostate epithelial cells, whose morbidity and mortality rates have been increasing every year. Although new drugs for treating prostate cancer continue to emerge, the unclear mechanism underlying drug targets limits this therapy, thereby constraining identification of effective therapeutic targets. Although GDP dissociation inhibitor 2(GDI2) is highly expressed and closely associated with occurrence and development of many tumors, its role in prostate cancer remains unclear. In this study, we investigated the role of GDI2 and elucidated its underlying mechanism of action in prostate cancer. Moreover, we screened chemotherapeutic drugs that affect GDI2 expression with a view of identifying novel targets for diagnosis and treatment of prostate cancer. METHODS: We performed sequence analyses and functional assays to precisely elucidate the GDI2 role in prostate cancer. Moreover, we induced tumorigenesis in nude mice to verify the role of GDI2 in vivo. Finally, we used the CCK8 assay to ascertain the most suitable IC50 across the three drugs and performed quantitative real time polymerase chain reaction (qRT-PCR) and Western Blot to analyze the effects of drugs on expression of GDI2, p75NTR, and p-NFκB. RESULTS: GDI2 was up-regulated in prostate cancer cells and tissues. Knocking down GDI2 suppressed cell proliferation but promoted cell apoptosis. Interestingly, knocking down GDI2 activated the p75NTR signaling pathway, indicating, for the first time, that p75NTR is negatively correlated with GDI2 expression. CONCLUSION: Taken together, these results indicate that GDI2 is a therapeutic target of paclitaxel. Knocking down of GDI2 inhibits cell proliferation and promotes cell apoptosis via the p75NTR signaling pathway in prostate cancer. Notably, paclitaxel inhibits GDI2 expression, implying that GDI2 may be a promising therapeutic target in prostate cancer.