Essential role of the small GTPase Ran in postnatal pancreatic islet development

Unlocking β-cell restoration: The crucial role of PDX1 in diabetes therapy

Diabetes has been a significant healthcare problem worldwide for a considerable period. The primary objective of diabetic treatment plans is to control the symptoms associated with the pathology. To effectively combat diabetes, it is crucial to comprehend the disease's etiology, essential factors, and the relevant processes involving β-cells. The development of the pancreas, maturation, and maintenance of β-cells, and their role in regular insulin function are all regulated by PDX1. Therefore, understanding the regulation of PDX1 and its interactions with signaling pathways involved in β-cell differentiation and proliferation are crucial elements of alternative diabetes treatment strategies. The present review aims to explore the protective role of PDX1 in β-cell proliferation through signaling pathways. The main keywords chosen for this review include "PDX1 for β-cell mass," "β-cell proliferation," "β-cell restoration via PDX1," and "mechanism of PDX1 in β-cells." A comprehensive literature search was conducted using various internet search engines, such as PubMed, Science Direct, and other publication databases. We summarize several approaches to generating β-cells from alternative cell sources, employing PDX1 under various modified growth conditions and different transcriptional factors. Our analysis highlights the unique potential of PDX1 as a promising target in molecular and cell-based therapies for diabetes.

Ran GTPase and Its Importance in Cellular Signaling and Malignant Phenotype

Ran is a member of the Ras superfamily of proteins, which primarily regulates nucleocytoplasmic trafficking and mediates mitosis by regulating spindle formation and nuclear envelope (NE) reassembly. Therefore, Ran is an integral cell fate determinant. It has been demonstrated that aberrant Ran expression in cancer is a result of upstream dysregulation of the expression of various factors, such as osteopontin (OPN), and aberrant activation of various signaling pathways, including the extracellular-regulated kinase/mitogen-activated protein kinase (ERK/MEK) and phosphatidylinositol 3-kinase/Protein kinase B (PI3K/Akt) pathways. In vitro, Ran overexpression has severe effects on the cell phenotype, altering proliferation, adhesion, colony density, and invasion. Therefore, Ran overexpression has been identified in numerous types of cancer and has been shown to correlate with tumor grade and the degree of metastasis present in various cancers. The increased malignancy and invasiveness have been attributed to multiple mechanisms. Increased dependence on Ran for spindle formation and mitosis is a consequence of the upregulation of these pathways and the ensuing overexpression of Ran, which increases cellular dependence on Ran for survival. This increases the sensitivity of cells to changes in Ran concentration, with ablation being associated with aneuploidy, cell cycle arrest, and ultimately, cell death. It has also been demonstrated that Ran dysregulation influences nucleocytoplasmic transport, leading to transcription factor misallocation. Consequently, patients with tumors that overexpress Ran have been shown to have a higher malignancy rate and a shorter survival time compared to their counterparts.

PDX-1: A Promising Therapeutic Target to Reverse Diabetes

The pancreatic duodenum homeobox-1 (PDX-1) is a transcription factor encoded by a Hox-like homeodomain gene that plays a crucial role in pancreatic development, β-cell differentiation, and the maintenance of mature β-cell functions. Research on the relationship between PDX-1 and diabetes has gained much attention because of the increasing prevalence of diabetes melitus (DM). Recent studies have shown that the overexpression of PDX-1 regulates pancreatic development and promotes β-cell differentiation and insulin secretion. It also plays a vital role in cell remodeling, gene editing, and drug development. Conversely, the absence of PDX-1 increases susceptibility to DM. Therefore, in this review, we summarized the role of PDX-1 in pancreatic development and the pathogenesis of DM. A better understanding of PDX-1 will deepen our knowledge of the pathophysiology of DM and provide a scientific basis for exploring PDX-1 as a potential target for treating diabetes.

Knockdown of Foxg1 in supporting cells increases the trans-differentiation of supporting cells into hair cells in the neonatal mouse cochlea

Foxg1 is one of the forkhead box genes that are involved in morphogenesis, cell fate determination, and proliferation, and Foxg1 was previously reported to be required for morphogenesis of the mammalian inner ear. However, Foxg1 knock-out mice die at birth, and thus the role of Foxg1 in regulating hair cell (HC) regeneration after birth remains unclear. Here we used Sox2CreER/+ Foxg1loxp/loxp mice and Lgr5-EGFPCreER/+ Foxg1loxp/loxp mice to conditionally knock down Foxg1 specifically in Sox2+ SCs and Lgr5+ progenitors, respectively, in neonatal mice. We found that Foxg1 conditional knockdown (cKD) in Sox2+ SCs and Lgr5+ progenitors at postnatal day (P)1 both led to large numbers of extra HCs, especially extra inner HCs (IHCs) at P7, and these extra IHCs with normal hair bundles and synapses could survive at least to P30. The EdU assay failed to detect any EdU+ SCs, while the SC number was significantly decreased in Foxg1 cKD mice, and lineage tracing data showed that much more tdTomato+ HCs originated from Sox2+ SCs in Foxg1 cKD mice compared to the control mice. Moreover, the sphere-forming assay showed that Foxg1 cKD in Lgr5+ progenitors did not significantly change their sphere-forming ability. All these results suggest that Foxg1 cKD promotes HC regeneration and leads to large numbers of extra HCs probably by inducing direct trans-differentiation of SCs and progenitors to HCs. Real-time qPCR showed that cell cycle and Notch signaling pathways were significantly down-regulated in Foxg1 cKD mice cochlear SCs. Together, this study provides new evidence for the role of Foxg1 in regulating HC regeneration from SCs and progenitors in the neonatal mouse cochlea.

GPCRs, G Proteins, and Their Impact on β-cell Function

Glucose-induced (physiological) insulin secretion from the islet β-cell involves interplay between cationic (i.e., changes in intracellular calcium) and metabolic (i.e., generation of hydrophobic and hydrophilic second messengers) events. A large body of evidence affirms support for novel regulation, by G proteins, of specific intracellular signaling events, including actin cytoskeletal remodeling, transport of insulin-containing granules to the plasma membrane for fusion, and secretion of insulin into the circulation. This article highlights the following aspects of GPCR-G protein biology of the islet. First, it overviews our current understanding of the identity of a wide variety of G protein regulators and their modulatory roles in GPCR-G protein-effector coupling, which is requisite for optimal β-cell function under physiological conditions. Second, it describes evidence in support of novel, noncanonical, GPCR-independent mechanisms of activation of G proteins in the islet. Third, it highlights the evidence indicating that abnormalities in G protein function lead to islet β-cell dysregulation and demise under the duress of metabolic stress and diabetes. Fourth, it summarizes observations of potential beneficial effects of GPCR agonists in preventing/halting metabolic defects in the islet β-cell under various pathological conditions (e.g., metabolic stress and inflammation). Lastly, it identifies knowledge gaps and potential avenues for future research in this evolving field of translational islet biology. Published 2020. Compr Physiol 10:453-490, 2020.

Association of Polymorphisms in miRNA Processing Genes With Type 2 Diabetes Mellitus and Its Vascular Complications in a Southern Chinese Population

Objective: To evaluate the potential association between the genetic variants in miRNA processing genes (RAN, XPO5, DICER1, and TARBP2) and susceptibility to type 2 diabetes mellitus (T2DM) and its vascular complications, as well as to further investigate their interaction with environmental factors in type 2 diabetes. Methods: We conducted a case-control study in genotyping of five polymorphic loci, including RAN rs14035, XPO5 rs11077, DICER1 rs13078, DICER1 rs3742330, and TARBP2 rs784567, in miRNA processing genes to explore the risk factors for T2DM and diabetic vascular complications. Haplotype analyses, interactions of gene-gene and interactions of gene-environment were performed too. Results: We identified a 36% decreased risk of developing T2DM in individuals with the minor A allele in DICER1 rs13078 (OR: 0.64; 95%CI: 0.42-0.95; P: 0.026). The AA haplotype in DICER1 was also associated with a protective effect on T2DM compared with the AT haplotype (OR: 0.63; 95%CI: 0.42-0.94; P-value: 0.023). T2DM patients with the TT+TC genotype at RAN rs14035 had a 1.89-fold higher risk of developing macrovascular complications than patients with the CC genotype (OR: 1.89; 95%CI: 1.04-3.45; P-value: 0.037). We also identified two three-factor interaction models. One is a three-factor [DICER1 rs13078, body mass index (BMI), and triglyceride (TG)] interaction model for T2DM (OR: 5.93; 95%CI: 1.25-28.26; P = 0.025). Another three-factor [RAN rs14035, hypertension (HP), and duration of T2DM (DOD)] interaction model was found for macrovascular complications of T2DM (OR = 41.60, 95%CI = 11.75-147.35, P < 0.001). Conclusion: Our study provides new evidence that two single nucleotide polymorphisms (SNPs) of the miRNA processing genes, DICER1 and RAN, and their interactions with certain environmental factors might contribute to the risk of T2DM and its vascular complications in the southern Chinese population.

Anti-Invasive and Anti-Proliferative Effects of shRNA-Loaded Poly(Lactide-Co-Glycolide) Nanoparticles Following RAN Silencing in MDA-MB231 Breast Cancer Cells

Background

Overexpression of the RAN GTP (RAN) gene has been shown to be linked to metastatic activity of MDA-MB231 human breast cancer cells by increasing Ras/MEK/ERK and PI3K/Akt/mTORC1 signalling. The aim of this study was to investigate the potential of polymeric nanoparticles to deliver two novel shRNA sequences, targeted against the RAN gene, to MDA-MB231 cells grown in culture and to assess their effects in a range of biological assays.

Methods

Biodegradable PLGA nanoparticles, loaded with shRNA-1 and shRNA-4, were fabricated using a double emulsion solvent evaporation technique and characterised for size, zeta potential and polydispersity index before testing on the MDA-MB231 cell line in a range of assays including cell viability, migration, invasion and gene knock down.

Results

shRNA-loaded nanoparticles were successfully fabricated and delivered to MDA-MB231 cells in culture, where they effectively released their payload, causing a decrease in both cell invasion and cell migration by knocking down RAN gene expression.

Conclusion

Results indicate the anti-RAN shRNA-loaded nanoparticles deliver and release biological payload to MDA-MB231 cells in culture. This works paves the way for further investigations into the possible use of anti-RAN shRNA-loaded NP formulations for the treatment of breast cancer in vivo.

Maternal stress predicts altered biogenesis and the profile of mitochondrial proteins in the frontal cortex and hippocampus of adult offspring rats

Currently, much attention is focused on the influence of mitochondrial disturbances at the onset of depression. The goal of this study was to investigate the impact of prenatal stress (an animal model of depression) on the mitochondrial biogenesis proteins and mitoproteome profile in the frontal cortex and hippocampus of adult 3-month-old male rats following a prenatal stress procedure. Our results show that rats that were exposed to prenatal stress stimuli displayed depression-like behaviors based on the sucrose preference and elevated plus maze tests. It has been found that the level of the PGC-1α protein was reduced in the frontal cortex and hippocampus of the adult offspring after the prenatal stress procedure. Moreover, in the frontal cortex, the level of the pro-apoptotic protein Bax was up-regulated. Two-dimensional electrophoresis coupled with mass spectrometry showed the statistically significant down-regulation of the mitochondrial ribosomal protein L12 (Mrpl12) and mitochondrial NADH dehydrogenase [ubiquinone] flavoprotein 2 (NDUFV2) as well as the up-regulation of the Tubulin Polymerization Promoting Proteins (Tppp/p25) in the frontal cortex. In contrast, in the hippocampus, the mitochondrial pyruvate dehydrogenase E1 component subunit beta, the voltage-dependent anion-selective channel protein 2 (VDAC2), and the GTP-binding nuclear protein RAN (RAN) were down-regulated and the expression of phosphatidylethanolamine-binding protein 1 (PEBP-1) was enhanced. These findings provide new evidence that stress during pregnancy may lead not only to behavioral deficits, but also to disturbances in the brain mitoproteome profile in adult rat offspring.