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RNA-binding protein HuD reduces triglyceride production in pancreatic β cells by enhancing the expression of insulin-induced gene 1.

ABSTRACT: Although triglyceride (TG) accumulation in the pancreas leads to β-cell dysfunction and raises the chance to develop metabolic disorders such as type 2 diabetes (T2DM), the molecular mechanisms whereby intracellular TG levels are regulated in pancreatic β cells have not been fully elucidated. Here, we present evidence that the RNA-binding protein HuD regulates TG production in pancreatic β cells. Mouse insulinoma βTC6 cells stably expressing a small hairpin RNA targeting HuD (shHuD) (βTC6-shHuD) contained higher TG levels compared to control cells. Moreover, downregulation of HuD resulted in a decrease in insulin-induced gene 1 (INSIG1) levels but not in the levels of sterol regulatory element-binding protein 1c (SREBP1c), a key transcription factor for lipid production. We identified Insig1 mRNA as a direct target of HuD by using ribonucleoprotein immunoprecipitation (RIP) and biotin pulldown analyses. By associating with the 3'-untranslated region (3'UTR) of Insig1 mRNA, HuD promoted INSIG1 translation; accordingly, HuD downregulation reduced while ectopic HuD expression increased INSIG1 levels. We further observed that HuD downregulation facilitated the nuclear localization of SREBP1c, thereby increasing the transcriptional activity of SREBP1c and the expression of target genes involved in lipogenesis; likewise, we observed lower INSIG1 levels in the pancreatic islets of HuD-null mice. Taken together, our results indicate that HuD functions as a novel repressor of lipid synthesis in pancreatic β cells.

SUBMITTER: Kim C

PROVIDER: S-EPMC8498970 | biostudies-literature |

REPOSITORIES: biostudies-literature

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RNA-binding protein HuD controls insulin translation.

Project description:Although expression of the mammalian RNA-binding protein HuD was considered to be restricted to neurons, we report that HuD is present in pancreatic β cells, where its levels are controlled by the insulin receptor pathway. We found that HuD associated with a 22-nucleotide segment of the 5' untranslated region (UTR) of preproinsulin (Ins2) mRNA. Modulating HuD abundance did not alter Ins2 mRNA levels, but HuD overexpression decreased Ins2 mRNA translation and insulin production, and conversely, HuD silencing enhanced Ins2 mRNA translation and insulin production. Following treatment with glucose, HuD rapidly dissociated from Ins2 mRNA and enabled insulin biosynthesis. Importantly, HuD-knockout mice displayed higher insulin levels in pancreatic islets, while HuD-overexpressing mice exhibited lower insulin levels in islets and in plasma. In sum, our results identify HuD as a pivotal regulator of insulin translation in pancreatic β cells.

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RNA binding protein HuD contributes to β-cell dysfunction by impairing mitochondria dynamics.

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Loss of RNA binding protein HuD facilitates the production of the senescence-associated secretory phenotype.

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The RNA-binding protein HuD regulates neuronal cell identity and maturation.

Project description:Neural Hu proteins (HuB/C/D) are RNA-binding proteins that have been shown to induce neuronal differentiation activity when overexpressed in immature neural progenitor cells or undifferentiated neuronal tumors. Newly generated HuD-deficient mice exhibited a transient impaired-cranial-nerve-development phenotype at an early embryonic stage. Adult HuD-deficient mice exhibited an abnormal hind-limb reflex and poor rotarod performance. Analysis of neurosphere formation revealed that the number and self-renewal capacity of the neural stem/progenitor cells were increased in HuD-deficient mice. HuD-deficient primary neurospheres also generated a smaller number of neurons. Cohort analysis of the cellular proliferative activity by using BrdUrd and iododeoxuridine labeling revealed that the number of differentiating quiescent cells in the embryonic cerebral wall was decreased. Long-term administration of BrdUrd revealed that the number of slowly dividing stem cells in the adult subventricular zone was increased in the HuD-deficient mice. Taken together, the results suggest that HuD is required at multiple points during neuronal development, including negative regulation of proliferative activity and neuronal cell-fate acquisition of neural stem/progenitor cells.

| S-EPMC555491 | biostudies-literature

Neuronal RNA-binding protein HuD regulates addiction-related gene expression and behavior.

Project description:The neuronal RNA-binding protein HuD is involved in synaptic plasticity and learning and memory mechanisms. These effects are thought to be due to HuD-mediated stabilization and translation of target mRNAs associated with plasticity. To investigate the potential role of HuD in drug addiction, we first used bioinformatics prediction algorithms together with microarray analyses to search for specific genes and functional networks upregulated within the forebrain of HuD overexpressing mice (HuDOE ). When this set was further limited to genes in the knowledgebase of addiction-related genes database (KARG) that contains predicted HuD-binding sites in their 3' untranslated regions (3'UTRs), we found that HuD regulates networks that have been associated with addiction-like behavior. These genes included Bdnf and Camk2a, 2 previously validated HuD targets. Since addiction is hypothesized to be a disorder stemming from altered gene expression causing aberrant plasticity, we sought to test the role of HuD in cocaine conditioned placed preference (CPP), a model of addiction-related behaviors. HuD mRNA and protein were upregulated by CPP within the nucleus accumbens of wild-type C57BL/6J mice. These changes were associated with increased expression of Bdnf and Camk2a mRNA and protein. To test this further, we trained HuDOE and wild-type mice in CPP and found that HuDOE mice showed increased cocaine CPP compared with controls. This was also associated with elevated expression of HuD target mRNAs and proteins, CaMKII? and BDNF. These findings suggest HuD involvement in addiction-related behaviors such as cocaine conditioning and seeking, through increased plasticity-related gene expression.

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Notch3 and the Notch3-upregulated RNA-binding protein HuD regulate Ikaros alternative splicing.

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