Siwanon Jirawatnotai

A function for cyclin D1 in DNA repair uncovered by protein interactome analyses in human cancers

Cyclin D1 is a component of the core cell cycle machinery. Abnormally high levels of cyclin D1 are detected in many human cancer types. To elucidate the molecular functions of cyclin D1 in human cancers, we performed a proteomic screen for cyclin D1 protein partners in several types of human tumours. Analyses of cyclin D1 interactors revealed a network of DNA repair proteins, including RAD51, a recombinase that drives the homologous recombination process. We found that cyclin D1 directly binds RAD51, and that cyclin D1–RAD51 interaction is induced by radiation. Like RAD51, cyclin D1 is recruited to DNA damage sites in a BRCA2-dependent fashion. Reduction of cyclin D1 levels in human cancer cells impaired recruitment of RAD51 to damaged DNA, impeded the homologous recombination-mediated DNA repair, and increased sensitivity of cells to radiation in vitro and in vivo. This effect was seen in cancer cells lacking the retinoblastoma protein, which do not require D-cyclins for proliferation. These findings reveal an unexpected function of a core cell cycle protein in DNA repair and suggest that targeting cyclin D1 may be beneficial also in retinoblastoma-negative cancers which are currently thought to be unaffected by cyclin D1 inhibition.

Transcriptional role of cyclin D1 in development revealed by a genetic-proteomic screen

Cyclin D1 belongs to the core cell cycle machinery, and it is frequently overexpressed in human cancers. The full repertoire of cyclin D1 functions in normal development and oncogenesis is unclear at present. Here we developed Flag- and haemagglutinin-tagged cyclin D1 knock-in mouse strains that allowed a high-throughput mass spectrometry approach to search for cyclin D1-binding proteins in different mouse organs. In addition to cell cycle partners, we observed several proteins involved in transcription. Genome-wide location analyses (chromatin immunoprecipitation coupled to DNA microarray; ChIP-chip) showed that during mouse development cyclin D1 occupies promoters of abundantly expressed genes. In particular, we found that in developing mouse retinas—an organ that critically requires cyclin D1 function—cyclin D1 binds the upstream regulatory region of the Notch1 gene, where it serves to recruit CREB binding protein (CBP) histone acetyltransferase. Genetic ablation of cyclin D1 resulted in decreased CBP recruitment, decreased histone acetylation of the Notch1 promoter region, and led to decreased levels of the Notch1 transcript and protein in cyclin D1-null (Ccnd1-/-) retinas. Transduction of an activated allele of Notch1 into Ccnd1-/- retinas increased proliferation of retinal progenitor cells, indicating that upregulation of Notch1 signalling alleviates the phenotype of cyclin D1-deficiency. These studies show that in addition to its well-established cell cycle roles, cyclin D1 has an in vivo transcriptional function in mouse development. Our approach, which we term ‘genetic–proteomic’, can be used to study the in vivo function of essentially any protein.

Curcumin Extract for Prevention of Type 2 Diabetes

OBJECTIVE To assess the efficacy of curcumin in delaying development of type 2 diabetes mellitus (T2DM) in the prediabetic population. RESEARCH DESIGN AND METHODS This randomized, double-blinded, placebo- controlled trial included subjects (n = 240) with criteria of prediabetes. All subjects were randomly assigned to receive either curcumin or placebo capsules for 9 months. To assess the T2DM progression after curcumin treatments and to determine the number of subjects progressing to T2DM, changes in β-cell functions (homeostasis model assessment [HOMA]-β, C-peptide, and proinsulin/insulin), insulin resistance (HOMA-IR), anti-inflammatory cytokine (adiponectin), and other parameters were monitored at the baseline and at 3-, 6-, and 9-month visits during the course of intervention. RESULTS After 9 months of treatment, 16.4% of subjects in the placebo group were diagnosed with T2DM, whereas none were diagnosed with T2DM in the curcumin-treated group. In addition, the curcumin-treated group showed a better overall function of β-cells, with higher HOMA-β (61.58 vs. 48.72; P < 0.01) and lower C-peptide (1.7 vs. 2.17; P < 0.05). The curcumin-treated group showed a lower level of HOMA-IR (3.22 vs. 4.04; P < 0.001) and higher adiponectin (22.46 vs. 18.45; P < 0.05) when compared with the placebo group. CONCLUSIONS A 9-month curcumin intervention in a prediabetic population significantly lowered the number of prediabetic individuals who eventually developed T2DM. In addition, the curcumin treatment appeared to improve overall function of β-cells, with very minor adverse effects. Therefore, this study demonstrated that the curcumin intervention in a prediabetic population may be beneficial.

Reduction of atherogenic risk in patients with type 2 diabetes by curcuminoid extract: a randomized controlled trial ☆

Curcumin is a phytocompound found in the root of turmeric, a common herbal ingredient in many Asian cuisines. The compound contains anti-inflammatory activity, which is mediated through an up-regulation of adiponectin and reduction of leptin. Consumption of curcumin was shown to prevent some deteriorative conditions caused by inflammation, such as ulcerative colitis, rheumatoid arthritis and esophagitis, and so on. Inflammation-associated cardiovascular conditions such as atherosclerosis are common in diabetes patients. The anti-inflammation effect of curcumin might be beneficial to prevent such condition in these patients. We aim to evaluate an antiatherosclerosis effect of curcumin in diabetes patients. Effects of curcumin on risk factors for atherosclerosis were investigated in a 6-month randomized, double-blinded and placebo-controlled clinical trial that included subjects diagnosed with type 2 diabetes. An atherosclerosis parameter, the pulse wave velocity, and other metabolic parameters in patients treated with placebo and curcumin were compared. Our results showed that curcumin intervention significantly reduced pulse wave velocity, increased level of serum adiponectin and decreased level of leptin. These results are associated with reduced levels of homeostasis model assessment-insulin resistance, triglyceride, uric acid, visceral fat and total body fat. In summary, a 6-month curcumin intervention in type 2 diabetic population lowered the atherogenic risks. In addition, the extract helped to improve relevant metabolic profiles in this high-risk population.

Proteomic Identification of a Direct Role for Cyclin D1 in DNA Damage Repair

The human CCND1 gene, which encodes the cell-cycle protein cyclin D1, is one of the most frequently amplified genes in human cancers. Cyclin D1 activates the cyclin-dependent kinases CDK4 and CDK6 and drives cell proliferation. Beyond the cell-cycle role, the full repertoire of cyclin D1 functions in cancer cells is still unclear. Emerging evidence indicates that cyclin D1 may play a role in DNA damage response. In this review, we discuss observations linking cyclin D1 to DNA damage repair and summarize our recent findings, which show a cyclin D1 function in homologous recombination-mediated DNA repair.

Ultraviolet Radiation-Induced Skin Aging: The Role of DNA Damage and Oxidative Stress in Epidermal Stem Cell Damage Mediated Skin Aging

Skin is the largest human organ. Skin continually reconstructs itself to ensure its viability, integrity, and ability to provide protection for the body. Some areas of skin are continuously exposed to a variety of environmental stressors that can inflict direct and indirect damage to skin cell DNA. Skin homeostasis is maintained by mesenchymal stem cells in inner layer dermis and epidermal stem cells (ESCs) in the outer layer epidermis. Reduction of skin stem cell number and function has been linked to impaired skin homeostasis (e.g., skin premature aging and skin cancers). Skin stem cells, with self-renewal capability and multipotency, are frequently affected by environment. Ultraviolet radiation (UVR), a major cause of stem cell DNA damage, can contribute to depletion of stem cells (ESCs and mesenchymal stem cells) and damage of stem cell niche, eventually leading to photoinduced skin aging. In this review, we discuss the role of UV-induced DNA damage and oxidative stress in the skin stem cell aging in order to gain insights into the pathogenesis and develop a way to reduce photoaging of skin cells.

Association between serum uric acid level and microalbuminuria to chronic vascular complications in Thai patients with type 2 diabetes

AIMS To investigate an association between serum uric acid/microalbuminuria and chronic micro/macro-vascular complications in type 2 diabetic patients. METHODS This cross-sectional study enrolled 608 patients with type 2 diabetes. All subjects were examined and basic information on health of the subjects was recorded for inclusion criteria. Several chemical parameters (fasting plasma glucose, triglyceride, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, uric acid, and microalbuminuria), and related chronic vascular complications were measured and recorded in data forms. RESULTS Logistic regressions were used to analyse odds ratios between uric acid/microalbuminuria levels and several chronic vascular complications. Prevalence of chronic vascular complications in T2DM patients, namely coronary arterial disease, cerebrovascular disease, diabetic nephropathy, diabetic retinopathy, and diabetic peripheral neuropathy was significantly correlated with increase of uric acid level [2.29 (1.01-5.2), 16.01 (4.74-54.09), 9.99 (4.4-22.8), 4.43 (1.3-15.1), 4.37 (1.5-12.9)], and of microalbuminuria level [7.0 (3.6-13.8), 3.2 (1.2-8.7), NA, 14.7 (5.1-42.7), 7.2 (2.9-17.7)]. CONCLUSION Both elevated uric acid and microalbuminuria levels were significantly associated with diabetic chronic micro/macro-vascular complications. Monitoring of uric acid and microalbuminuria levels provides a predictive value for a presence of chronic micro/macro-vascular complications in patients with type 2 diabetes.

The cyclin D1-CDK4 oncogenic interactome enables identification of potential novel oncogenes and clinical prognosis

Overexpression of cyclin D1 and its catalytic partner, CDK4, is frequently seen in human cancers. We constructed cyclin D1 and CDK4 protein interaction network in a human breast cancer cell line MCF7, and identified novel CDK4 protein partners. Among CDK4 interactors we observed several proteins functioning in protein folding and in complex assembly. One of the novel partners of CDK4 is FKBP5, which we found to be required to maintain CDK4 levels in cancer cells. An integrative analysis of the extended cyclin D1 cancer interactome and somatic copy number alterations in human cancers identified BAIAPL21 as a potential novel human oncogene. We observed that in several human tumor types BAIAPL21 is expressed at higher levels as compared to normal tissue. Forced overexpression of BAIAPL21 augmented anchorage independent growth, increased colony formation by cancer cells and strongly enhanced the ability of cells to form tumors in vivo. Lastly, we derived an Aggregate Expression Score (AES), which quantifies the expression of all cyclin D1 interactors in a given tumor. We observed that AES has a prognostic value among patients with ER-positive breast cancers. These studies illustrate the utility of analyzing the interactomes of proteins involved in cancer to uncover potential oncogenes, or to allow better cancer prognosis.

Inhibition of protein kinase C promotes dengue virus replication

BackgroundDengue virus (DENV) is a member of the Flaviviridae family, transmitted to human via mosquito. DENV infection is common in tropical areas and occasionally causes life-threatening symptoms. DENV contains a relatively short positive-stranded RNA genome, which encodes ten viral proteins. Thus, the viral life cycle is necessarily rely on or regulated by host factors.MethodsIn silico analyses in conjunction with in vitro kinase assay were used to study kinases that potentially phosphorylate DENV NS5. Potential kinase was inhibited or activated by a specific inhibitor (or siRNA), or an activator. Results of the inhibition and activation on viral entry/replication and host cell survival were examined.ResultsOur in silico analyses indicated that the non-structural protein 5 (NS5), especially the RNA-dependent RNA polymerase (RdRp) domain, contains conserved phosphorylation sites for protein kinase C (PKC). Phosphorylation of NS5 RdRp was further verified by PKC in vitro kinase assay. Inhibitions of PKC by a PKC-specific chemical inhibitor or siRNA suppressed NS5 phosphorylation in vivo, increased viral replication and reduced viability of the DENV-infected cells. In contrary, activation of PKC effectively suppressed intracellular viral number.ConclusionsThese results indicated that PKC may act as a restricting mechanism that modulates the DENV replication and represses the viral outburst in the host cells.

Nrf2 in keratinocytes modulates UVB-induced DNA damage and apoptosis in melanocytes through MAPK signaling

Abstract Responses of melanocytes (MC) to ultraviolet (UV) irradiation can be influenced by their neighbouring keratinocytes (KC). We investigated the role of Nrf2 in regulating paracrine effects of KC on UVB‐induced MC responses through phosphorylation of MAPKs in association with oxidative stress in primary human MC cocultured with primary human KC using a transwell co‐culture system and small‐interfering RNA‐mediated silencing of Nrf2 (siNrf2). The mechanisms by which Nrf2 modulated paracrine factors including &agr;‐melanocyte‐stimulating hormone (&agr;‐MSH) and paracrine effects of KC on UVB‐mediated apoptosis were also assessed. Our findings showed that co‐culture of MC with siNrf2‐transfected KC enhanced UVB‐mediated cyclobutane pyrimidine dimer (CPD) formation, apoptosis and oxidant formation, together with phosphorylation of ERK, JNK and p38 in MC. Treatment of MC with conditioned medium (CM) from Nrf2‐depleted KC also increased UVB‐mediated MC damage, suggesting that KC modulated UVB‐mediated MC responses via paracrine effects. Additionally, depletion of Nrf2 in KC suppressed UVB‐induced &agr;‐MSH levels as early as 30 min post‐irradiation, although pretreatment with N‐acetylcysteine (NAC) elevated its levels in CM from siNrf2‐transfected KC. Furthermore, NAC reversed the effect of CM from Nrf2‐depleted KC on UVB‐induced apoptosis and inflammatory response in MC. Our study demonstrates for the first time that KC provided a rescue effect on UVB‐mediated MC damage, although depletion of Nrf2 in KC reversed its protective effects on MC in a paracrine fashion in association with elevation of ROS levels and activation of MAPK pathways in MC. Nrf2 may indirectly regulate the paracrine effects of KC probably by affecting levels of the paracrine factor &agr;‐MSH via a ROS‐dependent mechanism. Graphical abstract Figure. No Caption available. HighlightsKC rescued MC from UVB‐induced DNA damage, apoptosis and inflammatory response.Depletion of Nrf2 in KC reversed its protective effects on MC via MAPK activation.Nrf2 may regulate paracrine protective effects of KC via a ROS‐dependent mechanism.