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The Journal of Biological Chemistry Jul 2023Insulin is made from proinsulin, but the extent to which fasting/feeding controls the homeostatically regulated proinsulin pool in pancreatic β-cells remains largely...
Insulin is made from proinsulin, but the extent to which fasting/feeding controls the homeostatically regulated proinsulin pool in pancreatic β-cells remains largely unknown. Here, we first examined β-cell lines (INS1E and Min6, which proliferate slowly and are routinely fed fresh medium every 2-3 days) and found that the proinsulin pool size responds to each feeding within 1 to 2 h, affected both by the quantity of fresh nutrients and the frequency with which they are provided. We observed no effect of nutrient feeding on the overall rate of proinsulin turnover as quantified from cycloheximide-chase experiments. We show that nutrient feeding is primarily linked to rapid dephosphorylation of translation initiation factor eIF2α, presaging increased proinsulin levels (and thereafter, insulin levels), followed by its rephosphorylation during the ensuing hours that correspond to a fall in proinsulin levels. The decline of proinsulin levels is blunted by the integrated stress response inhibitor, ISRIB, or by inhibition of eIF2α rephosphorylation with a general control nonderepressible 2 (not PERK) kinase inhibitor. In addition, we demonstrate that amino acids contribute importantly to the proinsulin pool; mass spectrometry shows that β-cells avidly consume extracellular glutamine, serine, and cysteine. Finally, we show that in both rodent and human pancreatic islets, fresh nutrient availability dynamically increases preproinsulin, which can be quantified without pulse-labeling. Thus, the proinsulin available for insulin biosynthesis is rhythmically controlled by fasting/feeding cycles.
Topics: Humans; Insulin; Insulin-Secreting Cells; Islets of Langerhans; Nutrients; Proinsulin; Stress, Physiological; Signal Transduction; Cell Line; Up-Regulation
PubMed: 37209827
DOI: 10.1016/j.jbc.2023.104836 -
Cellular & Molecular Biology Letters Jul 2023Sebaceous glands (SGs) synthesize and secret sebum to protect and moisturize the dermal system via the complicated endocrine modulation. Dysfunction of SG are usually...
BACKGROUND
Sebaceous glands (SGs) synthesize and secret sebum to protect and moisturize the dermal system via the complicated endocrine modulation. Dysfunction of SG are usually implicated in a number of dermal and inflammatory diseases. However, the molecular mechanism behind the differentiation, development and proliferation of SGs is far away to fully understand.
METHODS
Herein, the rat volar and mammary tissues with abundant SGs from female SD rats with (post-natal day (PND)-35) and without puberty onset (PND-25) were arrested, and conducted RNA sequencing. The protein complex of Neuropeptide Y receptor Y2 (NPY2R)/NPY5R/Nuclear factor of activated T cells 1 (NFATc1) was performed by immunoprecipitation, mass spectrum and gel filtration. Genome-wide occupancy of NFATc1 was measured by chromatin immunoprecipitation sequencing. Target proteins' expression and localization was detected by western blot and immunofluorescence.
RESULTS
NPY2R gene was significantly up-regulated in volar and mammary SGs of PND-25. A special protein complex of NPY2R/NPY5R/NFATc1 in PND-25. NFATc1 was dephosphorylated and activated, then localized into nucleus to exert as a transcription factor in volar SGs of PND-35. NFATc1 was especially binding at enhancer regions to facilitate the distal SG and sebum related genes' transcription. Dual specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) contributed to NFATc1 phosphorylation in PND-25, and inactivated of DYRK1A resulted in NFATc1 dephosphorylation and nuclear localization in PND-35.
CONCLUSIONS
Our findings unmask the new role of NPY2R/NFATc1/DYRK1A in pubertal SG, and are of benefit to advanced understanding the molecular mechanism of SGs' function after puberty, and provide some theoretical basis for the treatment of acne vulgaris from the perspective of hormone regulation.
Topics: Animals; Female; Rats; Acne Vulgaris; NFI Transcription Factors; Rats, Sprague-Dawley; Sebaceous Glands; Sebum; Dyrk Kinases
PubMed: 37501148
DOI: 10.1186/s11658-023-00467-4 -
A noncanonical function of SKP1 regulates the switch between autophagy and unconventional secretion.Science Advances Oct 2023Intracellular degradation of proteins and organelles by the autophagy-lysosome system is essential for cellular quality control and energy homeostasis. Besides...
Intracellular degradation of proteins and organelles by the autophagy-lysosome system is essential for cellular quality control and energy homeostasis. Besides degradation, endolysosomal organelles can fuse with the plasma membrane and contribute to unconventional secretion. Here, we identify a function for mammalian SKP1 in endolysosomes that is independent of its established role as an essential component of the family of SCF/CRL1 ubiquitin ligases. We found that, under nutrient-poor conditions, SKP1 is phosphorylated on Thr, allowing its interaction with V subunits of the vacuolar ATPase (V-ATPase). This event, in turn, promotes V-ATPase assembly to acidify late endosomes and enhance endolysosomal degradation. Under nutrient-rich conditions, SUMOylation of phosphorylated SKP1 allows its binding to and dephosphorylation by the PPM1B phosphatase. Dephosphorylated SKP1 interacts with SEC22B to promote unconventional secretion of the content of less acidified hybrid endosomal/autophagic compartments. Collectively, our study implicates SKP1 phosphorylation as a switch between autophagy and unconventional secretion in a manner dependent on cellular nutrient status.
Topics: Autophagy; Cell Membrane; Endosomes; Lysosomes; Vacuolar Proton-Translocating ATPases; Humans
PubMed: 37831778
DOI: 10.1126/sciadv.adh1134 -
JCI Insight Oct 2023Overexpression of phosphatases of regenerating liver 2 (PRL2), detected in numerous diverse cancers, is often associated with increased severity and poor patient...
Overexpression of phosphatases of regenerating liver 2 (PRL2), detected in numerous diverse cancers, is often associated with increased severity and poor patient prognosis. PRL2-catalyzed tyrosine dephosphorylation of the tumor suppressor PTEN results in increased PTEN degradation and has been identified as a mechanism underlying PRL2 oncogenic activity. Overexpression of PRL2, coincident with reduced PTEN protein, is frequently observed in patients with acute myeloid leukemia (AML). In the current study, a PTEN-knockdown AML animal model was generated to assess the effect of conditional PRL2 inhibition on the level of PTEN protein and the development and progression of AML. Inhibition of PRL2 resulted in a significant increase in median animal survival, from 40 weeks to greater than 60 weeks. The prolonged survival reflected delayed expansion of aberrantly differentiated hematopoietic stem cells into leukemia blasts, resulting in extended time required for clinically relevant leukemia blast accumulation in the BM niche. Leukemia blast suppression following PRL2 inhibition was correlated with an increase in PTEN and downregulation of AKT/mTOR-regulated pathways. These observations directly established, in a disease model, the viability of PRL2 inhibition as a therapeutic strategy for improving clinical outcomes in AML and potentially other PTEN-deficient cancers by slowing cancer progression.
Topics: Animals; Humans; Signal Transduction; PTEN Phosphohydrolase; Leukemia, Myeloid, Acute; Hematopoietic Stem Cells
PubMed: 37665633
DOI: 10.1172/jci.insight.170065 -
Cell Communication and Signaling : CCS Aug 2023The Annexin A6 (AnxA6) protein is known to inhibit the epidermal growth factor receptor (EGFR)-extracellular signal regulated kinase (ERK)1/2 signaling upon EGF...
BACKGROUND
The Annexin A6 (AnxA6) protein is known to inhibit the epidermal growth factor receptor (EGFR)-extracellular signal regulated kinase (ERK)1/2 signaling upon EGF stimulation. While the biochemical mechanism of AnxA6 inactivating phosphorylation of EGFR and ERK1/2 is not completely explored in cancer cells.
METHODS
Cells were transiently co-transfected with pFlag-AnxA6, pHA-UBC9 and pHis-SUMO1 plasmids to enrich the SUMOylated AnxA6 by immunoprecipitation, and the modification level of AnxA6 by SUMO1 was detected by Western blot against SUMO1 antibody. The SUMOylation level of AnxA6 was compared in response to chemical SUMOylation inhibitor treatment. AnxA6 SUMOylation sites were further identified by LC-MS/MS and amino acid site mutation validation. AnxA6 gene was silenced through AnxA6 targeting shRNA-containing pLKO.1 lentiviral transfection in HeLa cells, while AnxA6 gene was over-expressed within the Lenti-Vector carrying AnxA6 or mutant AnxA6 plasmid in A431 cells using lentiviral infections. Moreover, the mutant plasmid pGFP-EGFR was constructed to test AnxA6 regulation on EGFR mutation-induced signal transduction. Moreover, cell proliferation, migration, and gefitinib chemotherapy sensitivity were evaluated in HeLa and A431 cells under AnxA6 konckdown or AnxA6 overexpression by CCK8, colony form and wound healing assays. And tumorigenicity in vivo was measured in epithelial cancer cells-xenografted nude mouse model.
RESULTS
AnxA6 was obviously modified by SUMO1 conjugation within Lys (K) residues, and the K299 was one key SUMOylation site of AnxA6 in epithelial cancer cells. Compared to the wild type AnxA6, AnxA6 knockdown and its SUMO site mutant AnxA6 showed less suppression of dephosphorylation of EGFR-ERK1/2 under EGF stimulation. The SUMOylated AnxA6 was prone to bind EGFR in response to EGF inducement, which facilitated EGFR-PKCα complex formation to decrease the EGF-induced phosphorylation of EGFR-ERK1/2 and cyclin D1 expression. Similarly, AnxA6 SUMOylation inhibited dephosphorylation of the mutant EGFR, thereby impeding EGFR mutation-involved signal transduction. Moreover, AnxA6 knockdown or the K299 mutant AnxA6 conferred AnxA6 inability to suppress tumor progression, resulting in drug resistance to gefitinib in epithelial cancer cells. And in epithelial cancer cells-xenografted nude mouse model, both the weight and size of tumors derived from AnxA6 knockdown or AnxA6 mutation-expressing cells were much greater than that of AnxA6-expressing cells.
CONCLUSIONS
Besides EGFR gene mutation, protein SUMOylation modification of EGFR-binding protein AnxA6 also functions pivotal roles in mediating epithelial cancer cell growth and gefitinib drug effect. Video Abstract.
Topics: Humans; Animals; Mice; ErbB Receptors; Gefitinib; Annexin A6; Genes, erbB-1; HeLa Cells; Protein Kinase C-alpha; Sumoylation; Mice, Nude; Chromatography, Liquid; Epidermal Growth Factor; Cell Line, Tumor; Protein Kinase Inhibitors; Lung Neoplasms; Mutation; Tandem Mass Spectrometry
PubMed: 37528485
DOI: 10.1186/s12964-023-01217-x -
Frontiers in Plant Science 2024Plant phytochromes, renowned phosphoproteins, are red and far-red photoreceptors that regulate growth and development in response to light signals. Studies on... (Review)
Review
Plant phytochromes, renowned phosphoproteins, are red and far-red photoreceptors that regulate growth and development in response to light signals. Studies on phytochrome phosphorylation postulate that the N-terminal extension (NTE) and hinge region between N- and C-domains are sites of phosphorylation. Further studies have demonstrated that phosphorylation in the hinge region is important for regulating protein-protein interactions with downstream signaling partners, and phosphorylation in the NTE partakes in controlling phytochrome activity for signal attenuation and nuclear import. Moreover, phytochrome-associated protein phosphatases have been reported, indicating a role of reversible phosphorylation in phytochrome regulation. Furthermore, phytochromes exhibit serine/threonine kinase activity with autophosphorylation, and studies on phytochrome mutants with impaired or increased kinase activity corroborate that they are functional protein kinases in plants. In addition to the autophosphorylation, phytochromes negatively regulate PHYTOCHROME-INTERACTING FACTORs (PIFs) in a light-dependent manner by phosphorylating them as kinase substrates. Very recently, a few protein kinases have also been reported to phosphorylate phytochromes, suggesting new views on the regulation of phytochrome via phosphorylation. Using these recent advances, this review details phytochrome regulation through phosphorylation and highlights their significance as protein kinases in plant light signaling.
PubMed: 38545394
DOI: 10.3389/fpls.2024.1259720 -
Parkinson's Disease 2023To investigate the role of aberrant Dyrk1a expression in phosphorylation modification at the -synuclein serine 129 (Ser129) site to analyze its molecular mechanism in...
OBJECTIVE
To investigate the role of aberrant Dyrk1a expression in phosphorylation modification at the -synuclein serine 129 (Ser129) site to analyze its molecular mechanism in mediating apoptosis of PD.
METHODS
The protein level of P--synuclein (Ser129), -synuclein, Bcl-2, Bax, active caspase 3, GSK3, PI3K, AKT, and cyclinD1 were detected. The mRNA transcript levels of Dyrk1a and DAT and protein levels of IL-1, IL-6, COX-2, and TNF- were detected.
RESULTS
P--synuclein (Ser129), -synuclein, Bax, active caspase 3, GSK3, and cyclinD1 expressions were decreased in Dyrk1a-AAV-ShRNA ( < 0.05), and Bcl-2, AKT, and PI3K expressions were increased ( < 0.05). Increased TH protein expression was shown in Dyrk1a-AAV-ShRNA ( < 0.05). Dyrk1a mRNA was decreased in the Dyrk1a-AAV-ShRNA group ( < 0.05), and DAT mRNA was increased ( < 0.05). IL-1, IL-6, COX-2, and TNF- protein levels were decreased in Dyrk1al-AAV-Sh-RNA ( < 0.05). Transcriptome sequencing showed that Fam220a, which was expected to activate STAT family protein binding activity and participate in the negative regulation of transcription through RNA polymerase II and protein dephosphorylation showed differentially upregulated expression. The untargeted metabolome showed that the major compounds in the Dyrk1a-AAV-ShRNA group were hormones and transmission mediators and the most metabolism-related pathways. Fam220a showed differentially upregulated expression, and differentially expressed genes were enriched for the neuroactive ligand-receptor interaction, vascular smooth muscle contraction, and melanogenesis-related pathways.
CONCLUSION
Abnormal Dyrk1a expression can affect -synuclein phosphorylation modifications, and dyrk1a knockdown activates the PI3K/AKT pathway and reduces dopaminergic neuron apoptosis. It provides a theoretical basis for the group to further investigate the molecular mechanism.
PubMed: 37469393
DOI: 10.1155/2023/8848642 -
Life Science Alliance Aug 2023SLIT/ROBO signaling impacts many aspects of tissue development and homeostasis, in part, through the regulation of cell growth and proliferation. Recent studies have...
SLIT/ROBO signaling impacts many aspects of tissue development and homeostasis, in part, through the regulation of cell growth and proliferation. Recent studies have also linked SLIT/ROBO signaling to the regulation of diverse phagocyte functions. However, the mechanisms by which SLIT/ROBO signaling acts at the nexus of cellular growth control and innate immunity remain enigmatic. Here, we show that SLIT2-mediated activation of ROBO1 leads to inhibition of mTORC1 kinase activity in macrophages, leading to dephosphorylation of its downstream targets, including transcription factor EB and ULK1. Consequently, SLIT2 augments lysosome biogenesis, potently induces autophagy, and robustly promotes the killing of bacteria within phagosomes. Concordant with these results, we demonstrate decreased lysosomal content and accumulated peroxisomes in the spinal cords of embryos from , double knockout mice. We also show that impediment of auto/paracrine SLIT-ROBO signaling axis in cancer cells leads to hyperactivation of mTORC1 and inhibition of autophagy. Together, these findings elucidate a central role of chemorepellent SLIT2 in the regulation of mTORC1 activity with important implications for innate immunity and cancer cell survival.
Topics: Animals; Mice; Nerve Tissue Proteins; Receptors, Immunologic; Lysosomes; Bacteria; Mechanistic Target of Rapamycin Complex 1
PubMed: 37311584
DOI: 10.26508/lsa.202301964 -
The Journal of Clinical Investigation Nov 2023Dual-specificity phosphatase 8 (DUSP8) is a MAPK phosphatase that dephosphorylates and inactivates the kinase JNK. DUSP8 is highly expressed in T cells; however, the in...
Dual-specificity phosphatase 8 (DUSP8) is a MAPK phosphatase that dephosphorylates and inactivates the kinase JNK. DUSP8 is highly expressed in T cells; however, the in vivo role of DUSP8 in T cells remains unclear. Using T cell-specific Dusp8 conditional KO (T-Dusp8 cKO) mice, mass spectrometry analysis, ChIP-Seq, and immune analysis, we found that DUSP8 interacted with Pur-α, stimulated interleukin-9 (IL-9) gene expression, and promoted Th9 differentiation. Mechanistically, DUSP8 dephosphorylated the transcriptional repressor Pur-α upon TGF-β signaling, leading to the nuclear export of Pur-α and subsequent IL-9 transcriptional activation. Furthermore, Il-9 mRNA levels were induced in Pur-α-deficient T cells. In addition, T-Dusp8-cKO mice displayed reduction of IL-9 and Th9-mediated immune responses in the allergic asthma model. Reduction of Il-9 mRNA levels in T cells and allergic responses of T-Dusp8-cKO mice was reversed by Pur-α knockout. Remarkably, DUSP8 protein levels and the DUSP8-Pur-α interaction were indeed increased in the cytoplasm of T cells from people with asthma and patients with atopic dermatitis. Collectively, DUSP8 induces TGF-β-stimulated IL-9 transcription and Th9-induced allergic responses by inhibiting the nuclear translocation of the transcriptional repressor Pur-α. DUSP8 may be a T-cell biomarker and therapeutic target for asthma and atopic dermatitis.
Topics: Animals; Humans; Mice; Active Transport, Cell Nucleus; Asthma; Dermatitis, Atopic; Dual-Specificity Phosphatases; Hypersensitivity; Inflammation; Interleukin-9; RNA, Messenger; Transcription Factors; Transforming Growth Factor beta
PubMed: 37909329
DOI: 10.1172/JCI166269