Temperature-Dependent Upregulation of Per2 Protein Expression Is Mediated by eIF2α Kinases PERK and PKR through PI3K Activation.

Temperature-dependent translational control of the core clock gene Per2 plays an important role in establishing entrainment of the circadian clock to physiological body temperature cycles. Previously, we found an involvement of the phosphatidylinositol 3-kinase (PI3K) in causing Per2 protein expression in response to a warm temperature shift (WTS) within a physiological range (from 35 to 38.5 °C). However, signaling pathway mediating the Per2 protein expression in response to WTS is only sparsely understood. Additional factor(s) other than PI3K remains unknown. Here we report the identification of eukaryotic initiation factor 2α (eIF2α) kinases, protein kinase R (PKR) and PKR-like endoplasmic reticulum kinase (PERK), as a novel mediator of WTS-dependent Per2 protein expression. Canonically, eIF2α has been regarded as a major downstream target of PERK and PKR. However, we found that PERK and PKR mediate WTS response of Per2 in a manner not involving eIF2α. We observed that PERK and PKR serve as an upstream regulator of PI3K rather than eIF2α in the context of WTS-dependent Per2 protein expression. There have been studies reporting PI3K activation occurring depending on PERK and PKR, while its physiological contribution has remained elusive. Our finding therefore not only helps to enrich the knowledge of how WTS affects Per2 protein expression but also extends the region of cellular biology involving the PERK/PKR-mediated PI3K activation to include entrainment-mechanism of the circadian clock.

Abnormal ambiguous facial expression recognition in Chinese patients with schizophrenia.

BACKGROUND: Patients with schizophrenia (SCZ) exhibit difficulties deficits in recognizing facial expressions with unambiguous valence. However, only a limited number of studies have examined how these patients fare in interpreting facial expressions with ambiguous valence (for example, surprise). Thus, we aimed to explore the influence of emotional background information on the recognition of ambiguous facial expressions in SCZ. METHODS: A 3 (emotion: negative, neutral, and positive) × 2 (group: healthy controls and SCZ) experimental design was adopted in the present study. The experimental materials consisted of 36 images of negative emotions, 36 images of neutral emotions, 36 images of positive emotions, and 36 images of surprised facial expressions. In each trial, a briefly presented surprised face was preceded by an affective image. Participants (36 SCZ and 36 healthy controls (HC)) were required to rate their emotional experience induced by the surprised facial expressions. Participants' emotional experience was measured using the 9-point rating scale. The experimental data have been analyzed by conducting analyses of variances (ANOVAs) and correlation analysis. RESULTS: First, the SCZ group reported a more positive emotional experience under the positive cued condition compared to the negative cued condition. Meanwhile, the HC group reported the strongest positive emotional experience in the positive cued condition, a moderate experience in the neutral cued condition, and the weakest in the negative cue condition. Second, the SCZ (vs. HC) group showed longer reaction times (RTs) for recognizing surprised facial expressions. The severity of schizophrenia symptoms in the SCZ group was negatively correlated with their rating scores for emotional experience under neutral and positive cued condition. CONCLUSIONS: Recognition of surprised facial expressions was influenced by background information in both SCZ and HC, and the negative symptoms in SCZ. The present study indicates that the role of background information should be fully considered when examining the ability of SCZ to recognize ambiguous facial expressions.

Minimal upstream open reading frame of Per2 mediates phase fitness of the circadian clock to day/night physiological body temperature rhythm.

Body temperature in homeothermic animals does not remain constant but displays a regular circadian fluctuation within a physiological range (e.g., 35°C-38.5°C in mice), constituting a fundamental systemic signal to harmonize circadian clock-regulated physiology. Here, we find the minimal upstream open reading frame (uORF) encoded by the 5' UTR of the mammalian core clock gene Per2 and reveal its role as a regulatory module for temperature-dependent circadian clock entrainment. A temperature shift within the physiological range does not affect transcription but instead increases translation of Per2 through its minimal uORF. Genetic ablation of the Per2 minimal uORF and inhibition of phosphoinositide-3-kinase, lying upstream of temperature-dependent Per2 protein synthesis, perturb the entrainment of cells to simulated body temperature cycles. At the organismal level, Per2 minimal uORF mutant skin shows delayed wound healing, indicating that uORF-mediated Per2 modulation is crucial for optimal tissue homeostasis. Combined with transcriptional regulation, Per2 minimal uORF-mediated translation may enhance the fitness of circadian physiology.

Intracrine activity involving NAD-dependent circadian steroidogenic activity governs age-associated meibomian gland dysfunction.

Canonically, hormones are produced in the endocrine organs and delivered to target tissues. However, for steroids, the concept of tissue intracrinology, whereby hormones are produced in the tissues where they exert their effect without release into circulation, has been proposed, but its role in physiology/disease remains unclear. The meibomian glands in the eyelids produce oil to prevent tear evaporation, which reduces with aging. Here, we demonstrate that (re)activation of local intracrine activity through nicotinamide adenine dinucleotide (NAD+)-dependent circadian 3ß-hydroxyl-steroid dehydrogenase (3ß-HSD) activity ameliorates age-associated meibomian gland dysfunction and accompanying evaporative dry eye disease. Genetic ablation of 3ß-HSD nullified local steroidogenesis and led to atrophy of the meibomian gland. Conversely, reactivation of 3ß-HSD activity by boosting its coenzyme NAD+ availability improved glandular cell proliferation and alleviated the dry eye disease phenotype. Both women and men express 3ß-HSD in the meibomian gland. Enhancing local steroidogenesis may help combat age-associated meibomian gland dysfunction.

Time-Restricted G-Protein Signaling Pathways via GPR176, Gz, and RGS16 Set the Pace of the Master Circadian Clock in the Suprachiasmatic Nucleus.

G-protein-coupled receptors (GPCRs) are an important source of drug targets with diverse therapeutic applications. However, there are still more than one hundred orphan GPCRs, whose ligands and functions remain unidentified. The suprachiasmatic nucleus (SCN) is the central circadian clock of the brain, directing daily rhythms in activity-rest behavior and physiology. Malfunction of the circadian clock has been linked to a wide variety of diseases, including sleep-wake disorders, obesity, diabetes, cancer, and hypertension, making the circadian clock an intriguing target for drug development. The orphan receptor GPR176 is an SCN-enriched orphan GPCR that sets the pace of the circadian clock. GPR176 undergoes asparagine (N)-linked glycosylation, a post-translational modification required for its proper cell-surface expression. Although its ligand remains unknown, this orphan receptor shows agonist-independent basal activity. GPR176 couples to the unique G-protein subclass Gz (or Gx) and participates in reducing cAMP production during the night. The regulator of G-protein signaling 16 (RGS16) is equally important for the regulation of circadian cAMP synthesis in the SCN. Genome-wide association studies, employing questionnaire-based evaluations of individual chronotypes, revealed loci near clock genes and in the regions containing RGS16 and ALG10B, a gene encoding an enzyme involved in protein N-glycosylation. Therefore, increasing evidence suggests that N-glycosylation of GPR176 and its downstream G-protein signal regulation may be involved in pathways characterizing human chronotypes. This review argues for the potential impact of focusing on GPCR signaling in the SCN for the purpose of fine-tuning the entire body clock.