The protein kinase SIK downregulates the polarity protein Par3

Integrated bioinformatics analyses identifying potential biomarkers for type 2 diabetes mellitus and breast cancer: In SIK1-ness and health

The bidirectional causal relationship between type 2 diabetes mellitus (T2DM) and breast cancer (BC) has been established by numerous epidemiological studies. However, the underlying molecular mechanisms are not yet fully understood. Identification of hub genes implicated in T2DM-BC molecular crosstalk may help elucidate on the causative mechanisms. For this, expression series GSE29231 (T2DM-adipose tissue), GSE70905 (BC- breast adenocarcinoma biopsies) and GSE150586 (diabetes and BC breast biopsies) were extracted from Gene Expression Omnibus (GEO) database, and analyzed to obtain differentially expressed genes (DEGs). The overlapping DEGs were determined using FunRich. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and Transcription Factor (TF) analyses were performed on EnrichR software and a protein-protein interaction (PPI) network was constructed using STRING software. The network was analyzed on Cytoscape to determine hub genes and Kaplan-Meier plots were obtained. A total of 94 overlapping DEGs were identified between T2DM and BC samples. These DEGs were mainly enriched for GO terms RNA polymerase II core promoter proximal region sequence and its DNA binding, and cAMP response element binding protein, and KEGG pathways including bladder cancer, thyroid cancer and PI3K-AKT signaling. Eight hub genes were identified: interleukin 6 (IL6), tumor protein 53 (TP53), interleukin 8 (CXCL8), MYC, matrix metalloproteinase 9 (MMP9), beta-catenin 1 (CTNNB1), nitric oxide synthase 3 (NOS3) and interleukin 1 beta (IL1β). MMP9 and MYC associated unfavorably with overall survival (OS) in breast cancer patients, IL6, TP53, IL1β and CTNNB1 associated favorably, whereas NOS3 did not show any correlation with OS. Salt inducible kinase 1 (SIK1) was identified as a significant key DEG for comorbid samples when compared with BC, also dysregulated in T2DM and BC samples (adjusted p <0.05). Furthermore, four of the significant hub genes identified, including IL6, CXCL8, IL1B and MYC were also differentially expressed for comorbid samples, however at p < 0.05. Our study identifies key genes including SIK1, for comorbid state and 8 hub genes that may be implicated in T2DM-BC crosstalk. However, limitations associated with the insilico nature of this study necessitates for subsequent validation in wet lab. Hence, further investigation is crucial to study the molecular mechanisms of action underlying these genes to fully explore their potential as diagnostic and prognostic biomarkers and therapeutic targets for T2DM-BC association.

The salt-inducible kinases inhibitor HG-9-91-01 exhibits antidepressant-like actions in mice exposed to chronic unpredictable mild stress

Major depressive disorder is a frequently occurring neuropsychiatric disorder throughout the world. However, the limited and delayed therapeutic efficacy of monoaminergic medications has led to intensive research efforts to develop novel antidepressants. We have previously demonstrated that hippocampal salt-inducible kinase 2 (SIK2) plays a role in the pathogenesis of depression via regulating the downstream CREB-regulated transcription coactivator 1 (CRTC1)-cAMP response element-binding protein (CREB)-brain derived neurotrophic factor (BDNF) pathway. HG-9-91-01 is a potent and selective inhibitor of salt-inducible kinases (SIKs). The present study aims to explore whether HG-9-91-01 has antidepressant-like actions in male C57BL/6J mice. The chronic unpredictable mild stress (CUMS) model of depression, various behavioral tests, western blotting, co-immunoprecipitation, immunofluorescence, stereotactic infusion, and viral-mediated genetic knockdown were used together. It was found that hippocampal infusion of HG-9-91-01 induced significant antidepressant-like effects in the CUMS model, accompanied with preventing the enhancement of CUMS on the hippocampal SIK2 expression and cytoplasmic translocation of CRTC1. HG-9-91-01 treatment also reversed the decreasing effects of CUMS on the BDNF signaling cascade and adult neurogenesis in the hippocampus. Moreover, the antidepressant-like actions of HG-9-91-01 in mice required the hippocampal CRTC1-CREB-BDNF pathway. In conclusion, HG-9-91-01 has potential of being a novel antidepressant candidate.

SIKs suppress tumor function and regulate drug resistance in breast cancer

Salt-inducible kinases (SIKs), belonging to an AMP-activated kinase (AMPK) family, have an evolving role in tumourigenesis and metastasis in many solid tumours. However, the function of SIKs in breast cancer is not fully established. Here, we systematically elucidated the function of SIK family members in breast cancer. In clinical cohort of breast cancer, the expression of SIK1, SIK2 and SIK3 increased expression of SIKs was associated with good clinical outcome in breast cancer cohort. In vitro, reduced expression of SIK2 and SIK3, by way of knockdown increased the proliferation of breast cancer cells. However, SIK2 and SIK3 had contrasting effects on adhesion in breast cancer cells. Knockdown of SIK2 only enhanced the adhesion of triple negative breast cancer cell, while knockdown of SIK3 can decrease the adhesion of both MDA-MB-231 and MCF-7 cells. Interestingly, knockdown of SIK1 and SIK3 was seen to increase the invasion of MDA-MB-231 cells. Furthermore, reduced SIKs, even triple knockdown of SIK1, SIK2 and SIK3 rendered the breast cancer cells to confer chemoresistance to paclitaxel and cisplatin. Collectively, the study reports that SIKs are actively involved in regulating the aggressive functions of breast cancer cells and influence the clinical course of the patients with breast cancer that they molecules are potential prognostic factors and chemotherapy biomarkers.

The polarity protein PARD3 and cancer

Tissue disorganisation is one of the main hallmarks of cancer. Polarity proteins are responsible for the arrangement of cells within epithelial tissues through the asymmetric organisation of cellular components. Partition defective 3 (PARD3) is a master regulator of the Par polarity complex primarily due to its ability to form large complexes via its self-homologous binding domain. In addition to its role in polarity, PARD3 is a scaffolding protein that binds to intracellular signalling molecules, many of which are frequently deregulated in cancer. The role of PARD3 has been implicated in multiple solid cancers as either a tumour suppressor or promoter. This dual functionality is both physiologically and cell context dependent. In this review, we will discuss PARD3's role in tumourigenesis in both laboratory and clinical settings. We will also review several of the mechanisms underpinning PARD3's function including its association with intracellular signalling pathways and its role in the regulation of asymmetric cell division.

The Selective SIK2 Inhibitor ARN-3236 Produces Strong Antidepressant-Like Efficacy in Mice via the Hippocampal CRTC1-CREB-BDNF Pathway

Depression is a widespread chronic medical illness affecting thoughts, mood, and physical health. However, the limited and delayed therapeutic efficacy of monoaminergic drugs has led to intensive research efforts to develop novel antidepressants. ARN-3236 is the first potent and selective inhibitor of salt-inducible kinase 2 (SIK2). In this study, a multidisciplinary approach was used to explore the antidepressant-like actions of ARN-3236 in mice. Chronic social defeat stress (CSDS) and chronic unpredictable mild stress (CUMS) models of depression, various behavioral tests, high performance liquid chromatography-tandem mass spectrometry, stereotactic infusion, viral-mediated gene transfer, western blotting, co-immunoprecipitation and immunofluorescence were used together. It was found that ARN-3236 could penetrate the blood-brain barrier. Repeated ARN-3236 administration induced significant antidepressant-like effects in both the CSDS and CUMS models of depression, accompanied with fully preventing the stress-enhanced SIK2 expression and cytoplasmic translocation of cyclic adenosine monophosphate response element binding protein (CREB)-regulated transcription coactivator 1 (CRTC1) in the hippocampus. ARN-3236 treatment also completely reversed the down-regulating effects of CSDS and CUMS on the hippocampal brain-derived neurotrophic factor (BDNF) system and neurogenesis. Moreover, we demonstrated that the hippocampal CRTC1-CREB-BDNF pathway mediated the antidepressant-like efficacy of ARN-3236. Collectively, ARN-3236 possesses strong protecting effects against chronic stress, and could be a novel antidepressant beyond monoaminergic drugs.

The potent roles of salt-inducible kinases (SIKs) in metabolic homeostasis and tumorigenesis

Salt-inducible kinases (SIKs) belong to AMP-activated protein kinase (AMPK) family, and functions mainly involve in regulating energy response-related physiological processes, such as gluconeogenesis and lipid metabolism. However, compared with another well-established energy-response kinase AMPK, SIK roles in human diseases, especially in diabetes and tumorigenesis, are rarely investigated. Recently, the pilot roles of SIKs in tumorigenesis have begun to attract more attention due to the finding that the tumor suppressor role of LKB1 in non-small-cell lung cancers (NSCLCs) is unexpectedly mediated by the SIK but not AMPK kinases. Thus, here we tend to comprehensively summarize the emerging upstream regulators, downstream substrates, mouse models, clinical relevance, and candidate inhibitors for SIKs, and shed light on SIKs as the potential therapeutic targets for cancer therapies.

DEK1 displays a strong subcellular polarity during Physcomitrella patens 3D growth

Defective Kernel 1 (DEK1) is genetically at the nexus of the 3D morphogenesis of land plants. We aimed to localize DEK1 in the moss Physcomitrella patens to decipher its function during this process. To detect DEK1 in vivo, we inserted the tdTomato fluorophore into PpDEK1 gene locus. Confocal microscopy coupled with the use of time-gating allowed the precise DEK1 subcellular localization during 3D morphogenesis. DEK1 localization displays a strong polarized signal, as it is restricted to the plasma membrane domain between recently divided cells during the early steps of 3D growth development as well as during the subsequent vegetative growth. The signal furthermore displays a clear developmental pattern because it is only detectable in recently divided and elongating cells. Additionally, DEK1 localization appears to be independent of its calpain domain proteolytic activity. The DEK1 polar subcellular distribution in 3D tissue developing cells defines a functional cellular framework to explain its role in this developmental phase. Also, the observation of DEK1 during spermatogenesis suggests another biological function for this protein in plants. Finally the DEK1-tagged strain generated here provides a biological platform upon which further investigations into 3D developmental processes can be performed.

Salt Inducible Kinase Signaling Networks: Implications for Acute Kidney Injury and Therapeutic Potential

A number of signal transduction pathways are activated during Acute Kidney Injury (AKI). Of particular interest is the Salt Inducible Kinase (SIK) signaling network, and its effects on the Renal Proximal Tubule (RPT), one of the primary targets of injury in AKI. The SIK1 network is activated in the RPT following an increase in intracellular Na⁺ (Na⁺_in), resulting in an increase in Na,K-ATPase activity, in addition to the phosphorylation of Class IIa Histone Deacetylases (HDACs). In addition, activated SIKs repress transcriptional regulation mediated by the interaction between cAMP Regulatory Element Binding Protein (CREB) and CREB Regulated Transcriptional Coactivators (CRTCs). Through their transcriptional effects, members of the SIK family regulate a number of metabolic processes, including such cellular processes regulated during AKI as fatty acid metabolism and mitochondrial biogenesis. SIKs are involved in regulating a number of other cellular events which occur during AKI, including apoptosis, the Epithelial to Mesenchymal Transition (EMT), and cell division. Recently, the different SIK kinase isoforms have emerged as promising drug targets, more than 20 new SIK2 inhibitors and activators having been identified by MALDI-TOF screening assays. Their implementation in the future should prove to be important in such renal disease states as AKI.

Hippocampal Salt-Inducible Kinase 2 Plays a Role in Depression via the CREB-Regulated Transcription Coactivator 1-cAMP Response Element Binding-Brain-Derived Neurotrophic Factor Pathway

BACKGROUND

Developing novel pharmacological targets beyond monoaminergic systems is now a popular strategy for finding new ways to treat depression. Salt-inducible kinase (SIK) is a kinase that regulates the nuclear translocation of cyclic adenosine monophosphate response element binding protein (CREB)-regulated transcription coactivator (CRTC) by phosphorylation. Here, we hypothesize that dysfunction of the central SIK-CRTC system may contribute to the pathogenesis of depression.

METHODS

Chronic social defeat stress (CSDS) and chronic unpredictable mild stress (CUMS) models of depression, various behavioral tests, viral-mediated gene transfer, Western blotting, coimmunoprecipitation, quantitative real-time reverse transcription polymerase chain reaction, and immunohistochemistry were used in this study (for in vivo studies, n = 10; for in vitro studies, n = 5).

RESULTS

Both CSDS and CUMS markedly increased the expression of hippocampal SIK2, which reduced CRTC1 nuclear translocation and binding of CRTC1 and CREB in the hippocampus. Genetic overexpression of hippocampal SIK2 in naïve mice simulated chronic stress, inducing depressive-like behaviors in the forced swim test, tail suspension test, sucrose preference test, and social interaction test, as well as decreasing the brain-derived neurotrophic factor signaling cascade and neurogenesis in the hippocampus. In contrast, genetic knockdown and knockout of hippocampal SIK2 protected against CSDS and CUMS, exerting significant antidepressant-like effects that were mediated via the downstream CRTC1-CREB-brain-derived neurotrophic factor pathway. Moreover, fluoxetine, venlafaxine, and mirtazapine all significantly restored the effects of CSDS and CUMS on the hippocampal SIK2-CRTC1 pathway, which was necessary for their antidepressant actions.

CONCLUSIONS

The hippocampal SIK2-CRTC1 pathway is involved in the pathogenesis of depression, and hippocampal SIK2 could be a novel target for the development of antidepressants.

Epithelial-Mesenchymal Transition and Metastasis under the Control of Transforming Growth Factor β

Metastasis of tumor cells from primary sites of malignancy to neighboring stromal tissue or distant localities entails in several instances, but not in every case, the epithelial-mesenchymal transition (EMT). EMT weakens the strong adhesion forces between differentiated epithelial cells so that carcinoma cells can achieve solitary or collective motility, which makes the EMT an intuitive mechanism for the initiation of tumor metastasis. EMT initiates after primary oncogenic events lead to secondary secretion of cytokines. The interaction between tumor-secreted cytokines and oncogenic stimuli facilitates EMT progression. A classic case of this mechanism is the cooperation between oncogenic Ras and the transforming growth factor β (TGFβ). The power of TGFβ to mediate EMT during metastasis depends on versatile signaling crosstalk and on the regulation of successive waves of expression of many other cytokines and the progressive remodeling of the extracellular matrix that facilitates motility through basement membranes. Since metastasis involves many organs in the body, whereas EMT affects carcinoma cell differentiation locally, it has frequently been debated whether EMT truly contributes to metastasis. Despite controversies, studies of circulating tumor cells, studies of acquired chemoresistance by metastatic cells, and several (but not all) metastatic animal models, support a link between EMT and metastasis, with TGFβ, often being a common denominator in this link. This article aims at discussing mechanistic cases where TGFβ signaling and EMT facilitate tumor cell dissemination.