AMPK regulates immature boar Sertoli cell proliferation through affecting CDK4/Cyclin D3 pathway and mitochondrial function.

Sertoli cell (SC) proliferation plays an important role in sperm production and quality; however, the regulatory mechanism of SC proliferation is not well understood. This study investigated the role of adenosine monophosphate-activated protein kinase (AMPK) in the regulation of immature boar SC activity. Cell counting kit-8, Seahorse XFe96, mitochondrial respiratory enzyme-related assay kits, and transmission electron microscopy were used to detect SC proliferative viability, oxygen consumption rate (OCR), mitochondrial respiratory enzyme activity, and the ultrastructure of primary cultured SCs in vitro from the testes of 21-day-old boars. A dual luciferase reporter assay was performed to determine the miRNA-mRNA target interaction. Western blotting was used to analyze cell proliferation-related protein expression of p38, p21, proliferating cell nuclear antigen (PCNA), Cyclin-dependent kinase 4 (CDK4), Cyclin D3, and phosphorylated retinoblastoma protein (Rb). Each experiment had a completely randomized design, with three replicates in each experiment. The results showed that the AMPK inhibitor (Compound C, 20 µM-24 h) increased cell proliferation viability, ATP production, and maximal respiration of SCs by 0.64-, 0.12-, and 0.08-fold (p < 0.05), respectively; increased the SC protein expression of PCNA, CDK4, Cyclin D3, and p-Rb by 0.13-, 0.09-, 0.88-, and 0.12-fold (p < 0.05), respectively; and decreased the SC protein expression of p38 and p21 by 0.36- and 0.27-fold (p < 0.05), respectively. The AMPK agonist AICAR (2 mM-6 h) significantly inhibited SC ultrastructure, OCR, mitochondrial respiratory enzyme activity, and cell proliferation-related protein levels. AMPK was validated to be a target gene of miR-1285 based on the result in which the miR-1285 mimic inhibited the luciferase activity of wild-type AMPK by 0.54-fold (p < 0.001). MiR-1285 mimic promoted the OCR of SCs, with 0.45-, 0.15-, 0.21-, and 0.30-fold (p < 0.01) increases in ATP production, basal and maximal respiration, and spare capacity, respectively. MiR-1285 mimic increased the mitochondrial respiratory enzyme activity of SCs, with 0.63-, 0.70-, and 0.97-fold (p < 0.01) increases in NADH-Q oxidoreductase, cytochrome c oxidase, and ATP synthase, respectively. Moreover, the miR-1285 mimic increased the protein expression of PCNA, CDK4, Cyclin D3, and p-Rb by 0.24-, 0.30-, 0.22-, and 0.13-fold (p < 0.05), respectively, and reduced the protein expression of p38 and p21 by 0.58- and 0.66-fold (p < 0.001). MiR-1285 inhibitor showed opposite effects on the above indicators and induced numerous autophagosomes and large lipid droplets in SCs. A high dose of estradiol (10 µM-6 h, showed a promotion of AMPK activation in a previous study) significantly inhibited SC ultrastructure, mitochondrial function, and proliferation-related pathways, while these adverse effects were weakened by Compound C treatment or miR-1285 mimic transfection. Our findings suggest that the activation and inhibition of AMPK induced by specific drugs or synthesized targeted miRNA fragments could regulate immature boar SC proliferative activity by influencing the CDK4/Cyclin D3 pathway and mitochondrial function; this helps to provide a basis for the prevention and treatment of male sterility in clinical practice.

Forskolin-mediated cAMP activation upregulates TNF-α expression despite NF-κB downregulation in LPS-treated Schwann cells.

Although Schwann cells have been found to play a key role in inflammation and repair following nerve injury, the exact pathway is still unknown. To explore the mechanism by which Schwann cells exert their effects in the neuron microenvironment, we investigated two main inflammatory pathways: the NF-κB and cAMP pathways, and their downstream signaling molecules. In this study, lipopolysaccharide (LPS), a bacterial endotoxin, was used to activate the NF-κB pathway, and forskolin, a plant extract, was used to activate the cAMP pathway. The rat RT4-D6P2T Schwann cell line was treated with 0.1, 1, or 10 µg/mL of LPS, with or without 2 µM of forskolin, for 1, 3, 12, and 24 hours to determine the effects of elevated cAMP levels on LPS-treated cell viability. To investigate the effects of elevated cAMP levels on the expression of downstream signaling effector proteins, specifically NF-κB, TNF-α, AKAP95, and cyclin D3, as well as TNF-α secretion, RT4-D6P2T cells were incubated in the various treatment combinations for a 3-hour time period. Overall, results from the CellTiter-Glo viability assay revealed that forskolin increased viability in cells treated with smaller doses of LPS for 1 and 24 hours. For all time points, 10 µg/mL of LPS noticeably reduced viability regardless of forskolin treatment. Results from the Western blot analysis revealed that, at 10 µg/mL of LPS, forskolin upregulated the expression of TNF-α despite a downregulation of NF-κB, which was also accompanied by a decrease in TNF-α secretion. These results provide evidence that cAMP might regulate TNF-α expression through alternate pathways. Furthermore, although cAMP activation altered AKAP95 and cyclin D3 expression at different doses of LPS, there does not appear to be an association between the expression of AKAP95 or cyclin D3 and the expression of TNF-α. Exploring the possible interactions between cAMP, NF-κB, and other key inflammatory signaling pathways might reveal a potential therapeutic target for the treatment of nerve injury and inflammation.

Incidental Detection of TFEB-Amplified Renal Cell Carcinoma by Colocated Gene Amplification of CCND3 (6p21): A Case Report and Review of the Literature.

TFEB-amplified renal cell carcinoma (RCC), which belongs to the MITF family of RCC, is characterized by genomic amplification at the 6p21.1 locus where the TFEB gene is located. The vascular endothelial growth factor A and cyclin D3 genes are also located at this same locus. When tumors lack classic morphologic features, they may be classified as "RCC not otherwise specified (NOS)." However, it is increasingly important to accurately diagnose the RCC subtype to define the patient's individual prognosis and select the subsequent therapeutic modalities, which now include targeted agents. Therefore, knowledge of the diagnostic features of TFEB-altered RCCs, such as t(6;11) RCCs and TFEB-amplified RCCs, is critical for identifying these tumors. Herein, we present an interesting case of TFEB-amplified RCC that was initially diagnosed as RCC NOS on biopsy of a renal tumor in a community practice setting with available molecular findings demonstrating CCND3 amplification. The genetic abnormality was "accidentally" detected due to the amplification of the colocated CCND3 gene at the 6p21 locus of the TFEB gene on a limited genetic sequencing panel. This case highlights the importance of molecular tests in accurately diagnosing RCC and carefully interpreting molecular findings in the context of histomorphologic features.

Lipopolysaccharides of Brucella suis S2 Impaired the Process of Decidualization in Early Pregnancy in Mice.

Brucellosis is a notorious zoonotic disease caused by Brucella, which can lead to reproductive diseases in humans and animals, such as infertility and abortion. Lipopolysaccharides (LPS) are the main virulence factor of Brucella. LPS derived from Brucella are different and non-classical and are less toxic and less active than LPS isolated from E. coli. However, the effects and possible mechanisms of Brucella LPS-caused pregnancy loss remain to be revealed. In the present study, we investigated the effects of Brucella suis S2 LPS on early pregnancy loss in mice. The results indicated that embryo implantation failure was induced by Brucella LPS treatment in a dose-dependent manner. The injection of Brucella LPS mainly resulted in fibrinolysis in the decidual area of the uterus on the 6th day post coition (dpc), infiltration of large granular cells among the decidual cells near the embryo on the 8th dpc, a large number of gaps in the decidual area, and cell necrosis around the embryo. In addition, the expression of Cyclin D3 mRNA in the uterus on the 7th and 8th dpc and IGFBP-1 mRNA and the progesterone receptor in the uterus on the 6th and 7th dpc were also inhibited. Moreover, the expression of decidualization marker Cyclin D3 and decidualization prolactin-associated protein (dPRP) in endometrial stromal cells were also inhibited by Brucella LPS treatment in vitro. In summary, Brucella LPS affect the process of endometrial decidualization in mice by affecting the structure of the decidua and the expression of decidual marker factors in endometrial stromal cells.

Targeting diacylglycerol kinase α impairs lung tumorigenesis by inhibiting cyclin D3.

BACKGROUND: Diacylglycerol kinase α (DGKA) is the first member discovered from the diacylglycerol kinase family, and it has been linked to the progression of various types of tumors. However, it is unclear whether DGKA is linked to the development of lung cancer. METHODS: We investigated the levels of DGKA in the lung cancer tissues. Cell growth assay, colony formation assay and EdU assay were used to examine the effects of DGKA-targeted siRNAs/shRNAs/drugs on the proliferation of lung cancer cells in vitro. Xenograft mouse model was used to investigate the role of DGKA inhibitor ritanserin on the proliferation of lung cancer cells in vivo. The downstream target of DGKA in lung tumorigenesis was identified by RNA sequencing. RESULTS: DGKA is upregulated in the lung cancer cells. Functional assays and xenograft mouse model indicated that the proliferation ability of lung cancer cells was impaired after inhibiting DGKA. And cyclin D3(CCND3) is the downstream target of DGKA promoting lung cancer. CONCLUSIONS: Our study demonstrated that DGKA promotes lung tumorigenesis by regulating the CCND3 expression and hence it can be considered as a potential molecular biomarker to evaluate the prognosis of lung cancer patients. What's more, we also demonstrated the efficacy of ritanserin as a promising new medication for treating lung cancer.

Targeting protein tyrosine phosphatases for CDK6-induced immunotherapy resistance.

Elucidating the mechanisms of resistance to immunotherapy and developing strategies to improve its efficacy are challenging goals. Bioinformatics analysis demonstrates that high CDK6 expression in melanoma is associated with poor progression-free survival of patients receiving single-agent immunotherapy. Depletion of CDK6 or cyclin D3 (but not of CDK4, cyclin D1, or D2) in cells of the tumor microenvironment inhibits tumor growth. CDK6 depletion reshapes the tumor immune microenvironment, and the host anti-tumor effect depends on cyclin D3/CDK6-expressing CD8+ and CD4+ T cells. This occurs by CDK6 phosphorylating and increasing the activities of PTP1B and T cell protein tyrosine phosphatase (TCPTP), which, in turn, decreases tyrosine phosphorylation of CD3ζ, reducing the signal transduction for T cell activation. Administration of a PTP1B and TCPTP inhibitor prove more efficacious than using a CDK6 degrader in enhancing T cell-mediated immunotherapy. Targeting protein tyrosine phosphatases (PTPs) might be an effective strategy for cancer patients who resist immunotherapy treatment.

[LncRNA RPL22P1-201 affects prostate cancer cell proliferation, cell cycle, and sensitivity to docetaxel by regulating miR-216b-5p expression].

OBJECTIVE: Exploring the effects and mechanisms of long non coding RNA (lncRNA) RPL22P1-201 on prostate cancer cell proliferation, cell cycle, and docetaxel sensitivity by regulating miR-216b-5p expression. METHODS: The Cancer LncRNA Census database was used to analyze the differential expression of RPL22P1-201 between prostate cancer tissue and normal tissue. Real time quantitative polymerase chain reaction (qRT-PCR) was used to detect the expression level of RPL22P1-201 in prostate cancer cell lines (DU-145, C4-2B, PC3, 22Rv1, LNCaP) and normal prostate epithelial cells (RWPE-1). PC3 cells were divided into si-RPL22P1-201 group (transfected with RPL22P1-201 interference sequence) and si-NC group (transfected with si-NC sequence). Colony formation assay was used to detect the proliferation ability of PC3 cells. Flow cytometry was used to detect the PC3 cell cycle. The CCK-8 method was used to detect the proliferation of PC3 cells in each group after treatment with docetaxel. The dual luciferase reporter gene experiment verifies the binding of RPL22P1-201 to the target gene. qRT-PCR was used to detect the expression level of miR-216b-5p. Western blot was used to detect the expression levels of TrkB, CDK4, cyclin D2, cyclin D3, and CDK6 proteins. RESULTS: The expression level of RPL22P1-201 in prostate cancer tissue was higher than that in normal tissue (P<0.01). The expression level of RPL22P1-201 in prostate cancer cell lines was higher than that in normal prostate epithelial cells (P<0.01). The number of colonies in the si-NC group and si-RPL22P1-201 group was (256.1 ± 28.79) and (78.77 ± 14.52), respectively. The difference was statistically significant (P<0.01). The G0/G1 cell rates in the si-NC group and si-RPL22P1-201 group were (43.18 ± 4.56)% and (68.85 ± 3.40)%, respectively. The S cell rates were (36.84 ± 2.28)% and (24.27 ± 2.74)%, respectively. The G2/M cell rates were (19.98 ± 2.69)% and (6.88 ± 1.57)%, respectively, and the differences were statistically significant (all P<0.05). The cell survival rate of the si-RPL22P1-201 group under the action of docetaxel was lower than that of the si-NC group (all P<0.05). RPL22P1-201 can pair and bind with miR-216b-5p (P<0.01). Compared with the si-NC group, the si-RPL22P1-201 group showed a decrease in miR-216b-5p expression in PC3 cells (P<0.01), and a decrease in TrkB, CDK4, cyclin D2, cyclin D3, and CDK6 protein expression. CONCLUSIONS: RPL22P1-201 is highly expressed in prostate cancer, and silencing RPL22P1-201 inhibits prostate cancer PC3 cell proliferation and cell cycle by increasing miR-216b-5p expression, and enhances PC3 cell sensitivity to docetaxel.

Age- and cell cycle-related expression patterns of transcription factors and cell cycle regulators in Müller glia.

Mammalian Müller glia express transcription factors and cell cycle regulators essential for the function of retinal progenitors, indicating the latent neurogenic capacity; however, the role of these regulators remains unclear. To gain insights into the role of these regulators in Müller glia, we analyzed expression of transcription factors (Pax6, Vsx2 and Nfia) and cell cycle regulators (cyclin D1 and D3) in rodent Müller glia, focusing on their age- and cell cycle-related expression patterns. Expression of Pax6, Vsx2, Nfia and cyclin D3, but not cyclin D1, increased in Müller glia during development. Photoreceptor injury induced cell cycle-associated increase of Vsx2 and cyclin D1, but not Pax6, Nfia, and cyclin D3. In dissociated cultures, cell cycle-associated increase of Pax6 and Vsx2 was observed in Müller glia from P10 mice but not from P21 mice. Nfia levels were highly correlated with EdU incorporation suggesting their activation during S phase progression. Cyclin D1 and D3 were transiently upregulated in G1 phase but downregulated after S phase entry. Our findings revealed previously unknown links between cell cycle progression and regulator protein expression, which likely affect the cell fate decision of proliferating Müller glia.

Upregulation of KIF18B facilitates malignant phenotype of esophageal squamous cell carcinoma by activating CDCA8/mTORC1 pathway.

BACKGROUND: Kinesin family member 18B (KIF18B) has been regarded as an oncogene that is abnormally overexpressed in some cancers, but its mechanism in esophageal squamous cell carcinoma (ESCC) remains unclear, which is thereby investigated in this study. METHODS: Bioinformatics analysis was performed to analyze the expression of KIF18B in esophageal carcinoma (ESCA). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect KIF18B expression in ESCC cells. After KIF18B overexpression or cell division cycle associated 8 (CDCA8) deficiency, ESCC cells were subjected to determination of qRT-PCR, Western blot, cell counting kit-8 assay, flow cytometry, wound healing, and Transwell assay. The mechanism of KIF18B in the mechanistic target of rapamycin complex 1 (mTORC1) pathway was detected by Western blot. RESULTS: KIF18B was overexpressed in ESCA samples and ESCC cells. Upregulation of KIF18B enhanced the viability, accelerated cell cycle by elevating CDK4 and Cyclin D3 levels as well as promoted the migration and invasion by decreasing E-cadherin level and increasing Vimentin and N-cadherin levels in ESCC cells, which was counteracted by CDCA8 silencing. The expression of CDCA8 in ESCC cells was upregulated by KIF18B overexpression. KIF18B overexpression activated the mTORC1 pathway by upregulating phosphorylated (p)-/p70S6K and p-/mTOR levels in the ESCC cells, which was reversed by CDCA8 silencing. CONCLUSION: KIF18B overexpression promotes the proliferation, migration, and invasion of ESCC cells via CDCA8-mediated mTORC1 signaling pathway in vitro.

Early pregnancy exposure to beta-cypermethrin compromises endometrial decidualisation in mice via downregulation of cyclin D3, CDK4/6, and p21.

Beta-cypermethrin (ß-CYP) is a highly effective broad-spectrum insecticide that can potentially affect female reproduction. However, little is known about the effect of ß-CYP on uterine decidualisation, which is a vital process by which the uterus provides a suitable microenvironment for pregnancy maintenance. Therefore, we focused on the effect and mechanism of ß-CYP on endometrial decidualisation during early pregnancy in mice. The results indicated that the expression levels of HOXA10, BMP2, and IGFBP1 was significantly downregulated in the decidual tissue and primary endometrial stromal cells of pregnant and pseudopregnant mice following ß-CYP treatment. Serum E2 concentration was significantly increased, whereas P4 concentration and oestrogen receptor (ERα) and progesterone receptor (PRA) expression were significantly downregulated following ß-CYP exposure. The number of polyploid decidual cells was lower in the ß-CYP-treated group. Furthermore, ß-CYP significantly downregulated the protein expression levels of CDK4 and CDK6, and the mRNA expression levels of cyclin D3 and p21. The number of foetuses per female in the first litter was markedly reduced following exposure to ß-CYP. In summary, early pregnancy exposure to ß-CYP may result in defective endometrial decidualisation via compromised proliferation of uterine stromal cells and reduced expressions of cyclin D3, CDK4/6, and p21 in mice.

Mitochondrial ribosomal small subunit (MRPS) MRPS23 protein-protein interaction reveals phosphorylation by CDK11-p58 affecting cell proliferation and knockdown of MRPS23 sensitizes breast cancer cells to CDK1 inhibitors.

BACKGROUND: Post-translational modification of some mitoribosomal proteins has been found to regulate their functions. MRPS23 has been reported to be overexpressed in various cancers and has been predicted to be involved in increased cell proliferation. Furthermore, MRPS23 is a driver of luminal subtype breast cancer. However, its exact role and function in cancer remains unknown. METHODS AND RESULTS: Our previous study identified protein-protein interactions involving MRPS23 and CDK11A. In this study, we confirmed the interaction of MRPS23 with the p110 and p58 isoforms of CDK11A. Phosphoprotein enrichment studies and in vitro kinase assay using CDK11A/cyclin D3 followed by MALDI-ToF/ToF analysis confirmed the phosphorylation of MRPS23 at N-terminal serine 11 residue. Breast cancer cells expressing the MRPS23 (S11G) mutant showed increased cell proliferation, increased expression of PI3-AKT pathway proteins [p-AKT (Ser47), p-AKT (Thr308), p-PDK (Ser241) and p-GSK-3ß (Ser9)] and increased antiapoptotic pathway protein expression [Bcl-2, Bcl-xL, p-Bcl2 (Ser70) and MCL-1] when compared with the MRPS23 (S11A) mutant-overexpressing cells. This finding indicated the role of MRPS23 phosphorylation in the proliferation and survival of breast cancer cells. The correlation of inconsistent MRPS23 phosphoserine 11 protein expression with CDK11A in the breast cancer cells suggested phosphorylation by other kinases. In vitro kinase assay showed that CDK1 kinase also phosphorylated MRPS23 and that inhibition using CDK1 inhibitors lowered phospho-MRPS23 (Ser11) levels. Additionally, modulating the expression of MRPS23 altered the sensitivity of the cells to CDK1 inhibitors. CONCLUSION: In conclusion, phosphorylation of MRPS23 by mitotic kinases might potentially be involved in the proliferation of breast cancer cells. Furthermore, MRPS23 can be targeted for sensitizing the breast cancer cells to CDK1 inhibitors.

Hairy Cell Leukemia-Japanese Variant: Report of a Patient and Literature Review.

Hairy cell leukemia-Japanese variant (HCL-jv) shares some features with, but differs in other features from, HCL variant. Recently, it has been pointed out that HCL-jv and splenic diffuse red pulp small B-cell lymphoma (SDRPL) possibly constitute the same disease. We report a patient with HCL-jv, in which the neoplastic cells in the resected spleen were positive for CD11c, CD103, tartrate-resistant acid phosphatase (by immunohistochemistry), and weakly positive for cyclin D3. They were negative for CD25, CD123, annexin A1, and BRAF V600E-derived protein. Meta-analysis of HCL-jv cases in the literature showed considerable variation in the expression of HCL-related molecules. Although the clinical features and pattern of splenic involvement of HCL-jv are similar to those of SDRPL, some cytomorphological and phenotypical differences can be pointed out. To confirm whether the weak expression of cyclin D3 in our case suggests a spectrum from HCL-jv to SDRPL or one of the characteristics of HCL-jv, further studies on a large number of cases are necessary.

Keratin 19 interacts with GSK3ß to regulate its nuclear accumulation and degradation of cyclin D3.

Cyclin D3 regulates the G1/S transition and is frequently overexpressed in several cancer types including breast cancer, where it promotes tumor progression. Here we show that a cytoskeletal protein keratin 19 (K19) physically interacts with a serine/threonine kinase GSK3ß and prevents GSK3ß-dependent degradation of cyclin D3. The absence of K19 allowed active GSK3ß to accumulate in the nucleus and degrade cyclin D3. Specifically, the head (H) domain of K19 was required to sustain inhibitory phosphorylation of GSK3ß Ser9, prevent nuclear accumulation of GSK3ß, and maintain cyclin D3 levels and cell proliferation. K19 was found to interact with GSK3ß and K19-GSK3ß interaction was mapped out to require Ser10 and Ser35 residues on the H domain of K19. Unlike wildtype K19, S10A and S35A mutants failed to maintain total and nuclear cyclin D3 levels and induce cell proliferation. Finally, we show that the K19-GSK3ß-cyclin D3 pathway affected sensitivity of cells toward inhibitors to cyclin-dependent kinase 4 and 6 (CDK4/6). Overall, these findings establish a role for K19 in the regulation of GSK3ß-cyclin D3 pathway and demonstrate a potential strategy for overcoming resistance to CDK4/6 inhibitors.

Overexpression Populus d-Type Cyclin Gene PsnCYCD1;1 Influences Cell Division and Produces Curved Leaf in Arabidopsis thaliana.

d-type cyclins (CYCDs) are a special class of cyclins and play extremely important roles in plant growth and development. In the plant kingdom, most of the existing studies on CYCDs have been done on herbaceous plants, with few on perennial woody plants. Here, we identified a Populus d-type cyclin gene, PsnCYCD1;1, which is mainly transcribed in leaf buds and stems. The promoter of PsnCYCD1;1 activated GUS gene expression and transgenic Arabidopsis lines were strongly GUS stained in whole seedlings and mature anthers. Moreover, subcellular localization analysis showed the fluorescence signal of PsnCYCD1;1-GFP fusion protein is present in the nucleus. Furthermore, overexpression of the PsnCYCD1;1 gene in Arabidopsis can promote cell division and lead to small cell generation and cytokinin response, resulting in curved leaves and twisted inflorescence stems. Moreover, the transcriptional levels of endogenous genes, such as ASs, KNATs, EXP10, and PHB, were upregulated by PsnCYCD1;1. Together, our results indicated that PsnCYCD1;1 participates in cell division by cytokinin response, providing new information on controlling plant architecture in woody plants.

CRL4AMBRA1 is a master regulator of D-type cyclins.

D-type cyclins are central regulators of the cell division cycle and are among the most frequently deregulated therapeutic targets in human cancer1, but the mechanisms that regulate their turnover are still being debated2,3. Here, by combining biochemical and genetics studies in somatic cells, we identify CRL4AMBRA1 (also known as CRL4DCAF3) as the ubiquitin ligase that targets all three D-type cyclins for degradation. During development, loss of Ambra1 induces the accumulation of D-type cyclins and retinoblastoma (RB) hyperphosphorylation and hyperproliferation, and results in defects of the nervous system that are reduced by treating pregnant mice with the FDA-approved CDK4 and CDK6 (CDK4/6) inhibitor abemaciclib. Moreover, AMBRA1 acts as a tumour suppressor in mouse models and low AMBRA1 mRNA levels are predictive of poor survival in cancer patients. Cancer hotspot mutations in D-type cyclins abrogate their binding to AMBRA1 and induce their stabilization. Finally, a whole-genome, CRISPR-Cas9 screen identified AMBRA1 as a regulator of the response to CDK4/6 inhibition. Loss of AMBRA1 reduces sensitivity to CDK4/6 inhibitors by promoting the formation of complexes of D-type cyclins with CDK2. Collectively, our results reveal the molecular mechanism that controls the stability of D-type cyclins during cell-cycle progression, in development and in human cancer, and implicate AMBRA1 as a critical regulator of the RB pathway.

CDK11 Promotes Cytokine-Induced Apoptosis in Pancreatic Beta Cells Independently of Glucose Concentration and Is Regulated by Inflammation in the NOD Mouse Model.

Background: Pancreatic islets are exposed to strong pro-apoptotic stimuli: inflammation and hyperglycemia, during the progression of the autoimmune diabetes (T1D). We found that the Cdk11(Cyclin Dependent Kinase 11) is downregulated by inflammation in the T1D prone NOD (non-obese diabetic) mouse model. The aim of this study is to determine the role of CDK11 in the pathogenesis of T1D and to assess the hierarchical relationship between CDK11 and Cyclin D3 in beta cell viability, since Cyclin D3, a natural ligand for CDK11, promotes beta cell viability and fitness in front of glucose. Methods: We studied T1D pathogenesis in NOD mice hemideficient for CDK11 (N-HTZ), and, in N-HTZ deficient for Cyclin D3 (K11HTZ-D3KO), in comparison to their respective controls (N-WT and K11WT-D3KO). Moreover, we exposed pancreatic islets to either pro-inflammatory cytokines in the presence of increasing glucose concentrations, or Thapsigargin, an Endoplasmic Reticulum (ER)-stress inducing agent, and assessed apoptotic events. The expression of key ER-stress markers (Chop, Atf4 and Bip) was also determined. Results: N-HTZ mice were significantly protected against T1D, and NS-HTZ pancreatic islets exhibited an impaired sensitivity to cytokine-induced apoptosis, regardless of glucose concentration. However, thapsigargin-induced apoptosis was not altered. Furthermore, CDK11 hemideficiency did not attenuate the exacerbation of T1D caused by Cyclin D3 deficiency. Conclusions: This study is the first to report that CDK11 is repressed in T1D as a protection mechanism against inflammation-induced apoptosis and suggests that CDK11 lies upstream Cyclin D3 signaling. We unveil the CDK11/Cyclin D3 tandem as a new potential intervention target in T1D.

Overexpression of PtoCYCD3;3 Promotes Growth and Causes Leaf Wrinkle and Branch Appearance in Populus.

D-type cyclin (cyclin D, CYCD), combined with cyclin-dependent kinases (CDKs), participates in the regulation of cell cycle G1/S transition and plays an important role in cell division and proliferation. CYCD could affect the growth and development of herbaceous plants, such as Arabidopsis thaliana, by regulating the cell cycle process. However, its research in wood plants (e.g., poplar) is poor. Phylogenetic analysis showed that in Populus trichocarpa, CYCD3 genes expanded to six members, namely PtCYCD3;1-6. P. tomentosa CYCD3 genes were amplified based on the CDS region of P. trichocarpa CYCD3 genes. PtoCYCD3;3 showed the highest expression in the shoot tip, and the higher expression in young leaves among all members. Therefore, this gene was selected for further study. The overexpression of PtoCYCD3;3 in plants demonstrated obvious morphological changes during the observation period. The leaves became enlarged and wrinkled, the stems thickened and elongated, and multiple branches were formed by the plants. Anatomical study showed that in addition to promoting the differentiation of cambium tissues and the expansion of stem vessel cells, PtoCYCD3;3 facilitated the division of leaf adaxial epidermal cells and palisade tissue cells. Yeast two-hybrid experiment exhibited that 12 PtoCDK proteins could interact with PtoCYCD3;3, of which the strongest interaction strength was PtoCDKE;2, whereas the weakest was PtoCDKG;3. Molecular docking experiments further verified the force strength of PtoCDKE;2 and PtoCDKG;3 with PtoCYCD3;3. In summary, these results indicated that the overexpression of PtoCYCD3;3 significantly promoted the vegetative growth of Populus, and PtoCYCD3;3 may interact with different types of CDK proteins to regulate cell cycle processes.

Fbxl8 suppresses lymphoma growth and hematopoietic transformation through degradation of cyclin D3.

Overexpression of D-type cyclins in human cancer frequently occurs as a result of protein stabilization, emphasizing the importance of identification of the machinery that regulates their ubiqutin-dependent degradation. Cyclin D3 is overexpressed in ~50% of Burkitt's lymphoma correlating with a mutation of Thr-283. However, the E3 ligase that regulates phosphorylated cyclin D3 and whether a stabilized, phosphorylation deficient mutant of cyclin D3, has oncogenic activity are undefined. We describe the identification of SCF-Fbxl8 as the E3 ligase for Thr-283 phosphorylated cyclin D3. SCF-Fbxl8 poly-ubiquitylates p-Thr-283 cyclin D3 targeting it to the proteasome. Functional investigation demonstrates that Fbxl8 antagonizes cell cycle progression, hematopoietic cell proliferation, and oncogene-induced transformation through degradation of cyclin D3, which is abolished by expression of cyclin D3T283A, a non-phosphorylatable mutant. Clinically, the expression of cyclin D3 is inversely correlated with the expression of Fbxl8 in lymphomas from human patients implicating Fbxl8 functions as a tumor suppressor.

Cyclin D3 Governs Clonal Expansion of Dark Zone Germinal Center B Cells.

Germinal center (GC) B cells surge in their proliferative capacity, which poses a direct risk for B cell malignancies. G1- to S-phase transition is dependent on the expression and stability of D-type cyclins. We show that cyclin D3 expression specifically regulates dark zone (DZ) GC B cell proliferation. B cell receptor (BCR) stimulation of GC B cells downregulates cyclin D3 but induces c-Myc, which subsequently requires cyclin D3 to exert GC expansion. Control of DZ proliferation requires degradation of cyclin D3, which is dependent on phosphorylation of residue Thr283 and can be bypassed by cyclin D3T283A hyperstabilization as observed in B cell lymphoma. Thereby, selected GC B cells in the light zone potentially require disengagement from BCR signaling to accumulate cyclin D3 and undergo clonal expansion in the DZ.

Phospholipase C beta1 (PI-PLCbeta1)/Cyclin D3/protein kinase C (PKC) alpha signaling modulation during iron-induced oxidative stress in myelodysplastic syndromes (MDS).

MDS are characterized by anemia and transfusion requirements. Transfused patients frequently show iron overload that negatively affects hematopoiesis. Iron chelation therapy can be effective in these MDS cases, but the molecular consequences of this treatment need to be further investigated. That is why we studied the molecular features of iron effect and Deferasirox therapy on PI-PLCbeta1 inositide signaling, using hematopoietic cells and MDS samples. At baseline, MDS patients showing a positive response after iron chelation therapy displayed higher levels of PI-PLCbeta1/Cyclin D3/PKCalpha expression. During treatment, these responder patients, as well as hematopoietic cells treated with FeCl3 and Deferasirox, showed a specific reduction of PI-PLCbeta1/Cyclin D3/PKCalpha expression, indicating that this signaling pathway is targeted by Deferasirox. The treatment was also able to specifically decrease the production of ROS. This effect correlated with a reduction of IL-1A and IL-2, as well as Akt/mTOR phosphorylation. In contrast, cells exposed only to FeCl3 and cells from MDS patients refractory to Deferasirox showed a specific increase of ROS and PI-PLCbeta1/Cyclin D3/PKCalpha expression. All in all, our data show that PI-PLCbeta1 signaling is a target for iron-induced oxidative stress and suggest that baseline PI-PLCbeta1 quantification could predict iron chelation therapy response in MDS.