A family of LIM-only transcriptional coactivators: tissue-specific expression and selective activation of CREB and CREM

Unraveling the role of the FHL family in cardiac diseases: Mechanisms, implications, and future directions

Heart diseases are a major cause of morbidity and mortality worldwide. Understanding the molecular mechanisms underlying these diseases is essential for the development of effective diagnostic and therapeutic strategies. The FHL family consists of five members: FHL1, FHL2, FHL3, FHL4, and FHL5/Act. These members exhibit different expression patterns in various tissues including the heart. FHL family proteins are implicated in cardiac remodeling, regulation of metabolic enzymes, and cardiac biomechanical stress perception. A large number of studies have explored the link between FHL family proteins and cardiac disease, skeletal muscle disease, and ovarian metabolism, but a comprehensive and in-depth understanding of the specific molecular mechanisms targeting FHL on cardiac disease is lacking. The aim of this review is to explore the structure and function of FHL family members, to comprehensively elucidate the mechanisms by which they regulate the heart, and to explore in depth the changes in FHL family members observed in different cardiac disorders, as well as the effects of mutations in FHL proteins on heart health.

Expression Dynamics Indicate Potential Roles of KIF17 for Nuclear Reshaping and Tail Formation during Spermiogenesis in Phascolosoma esculenta

Kinesin family member17 (KIF17), a homologous dimer of the kinesin-2 protein family, has important microtubule-dependent and -independent roles in spermiogenesis. Little is known about KIF17 in the mollusk, Phascolosoma esculenta, a newly developed mariculture species in China. Here, we cloned the open reading frame of Pe-kif17 and its related gene, Pe-act, and performed bioinformatics analysis on both. Pe-KIF17 and Pe-ACT are structurally conserved, indicating that they may be functionally conserved. The expression pattern of kif17/act mRNA performed during spermiogenesis revealed their expression in diverse tissues, with the highest expression level in the coelomic fluid of P. esculenta. The expressions of Pe-kif17 and Pe-act mRNA were relatively high during the breeding season (July-September), suggesting that Pe-KIF17/ACT may be involved in spermatogenesis, particularly during spermiogenesis. Further analysis of Pe-kif17 mRNA via fluorescence in situ hybridization revealed the continuous expression of this mRNA during spermiogenesis, suggesting potential functions in this process. Immunofluorescence showed that Pe-KIF17 co-localized with α-tubulin and migrated from the perinuclear cytoplasm to one side of the spermatid, forming the sperm tail. Pe-KIF17 and Pe-ACT also colocalized. KIF17 may participate in spermiogenesis of P. esculenta, particularly in nuclear reshaping and tail formation by interacting with microtubule structures similar to the manchette. Moreover, Pe-KIF17 with Pe-ACT is also involved in nuclear reshaping and tail formation in the absence of microtubules. This study provides evidence for the role of KIF17 during spermiogenesis and provides theoretical data for studies of the reproductive biology of P. esculenta. These findings are important for spermatogenesis in mollusks.

The roles of FHL2 in cancer

LIM domain protein 2, also known as LIM protein FHL2, is a member of the LIM-only family. Due to its LIM domain protein characteristics, FHL2 is capable of interacting with various proteins and plays a crucial role in regulating gene expression, cell growth, and signal transduction in muscle and cardiac tissue. In recent years, mounting evidence has indicated that the FHLs protein family is closely associated with the development and occurrence of human tumors. On the one hand, FHL2 acts as a tumor suppressor by down-regulating in tumor tissue and effectively inhibiting tumor development by limiting cell proliferation. On the other hand, FHL2 serves as an oncoprotein by up-regulating in tumor tissue and binding to multiple transcription factors to suppress cell apoptosis, stimulate cell proliferation and migration, and promote tumor progression. Therefore, FHL2 is considered a double-edged sword in tumors with independent and complex functions. This article reviews the role of FHL2 in tumor occurrence and development, discusses FHL2 interaction with other proteins and transcription factors, and its involvement in multiple cell signaling pathways. Finally, the clinical significance of FHL2 as a potential target in tumor therapy is examined.

Transcription factor E4F1 as a regulator of cell life and disease progression

E4F transcription factor 1 (E4F1), a member of the GLI-Kruppel family of zinc finger proteins, is now widely recognized as a transcription factor. It plays a critical role in regulating various cell processes, including cell growth, proliferation, differentiation, apoptosis and necrosis, DNA damage response, and cell metabolism. These processes involve intricate molecular regulatory networks, making E4F1 an important mediator in cell biology. Moreover, E4F1 has also been implicated in the pathogenesis of a range of human diseases. In this review, we provide an overview of the major advances in E4F1 research, from its first report to the present, including studies on its protein domains, molecular mechanisms of transcriptional regulation and biological functions, and implications for human diseases. We also address unresolved questions and potential research directions in this field. This review provides insights into the essential roles of E4F1 in human health and disease and may pave the way for facilitating E4F1 from basic research to clinical applications.

The feedback loop of AURKA/DDX5/TMEM147-AS1/let-7 drives lipophagy to induce cisplatin resistance in epithelial ovarian cancer

Platinum-taxane chemotherapy is the first-line standard-of-care treatment administered to patients with epithelial ovarian cancer (EOC), and faces the major challenge of cisplatin resistance. Aurora Kinase A (AURKA) is a serine/threonine kinase, acting as an oncogene by participating in microtubule formation and stabilization. In this study, we demonstrate that AURKA binds with DDX5 directly to form a transcriptional coactivator complex to induce the transcription and upregulation of an oncogenic long non-coding RNA, TMEM147-AS1, which sponges hsa-let-7b/7c-5p leading to the increasing expression of AURKA as a feedback loop. The feedback loop maintains EOC cisplatin resistance via activation of lipophagy. These findings underscore the feedback loop of AURKA/DDX5/TMEM147-AS1/let-7 provides mechanistic insights into the combined use of TMEM147-AS1 siRNA and VX-680, which can help improve EOC cisplatin treatment. Our mathematical model shows that the feedback loop has the potential to act as a biological switch to maintain on- (activated) or off- (deactivated) status, implying the possible resistance of single use of VX-680 or TMEM147-AS1 siRNA. The combined use reduces both the protein level of AURKA using TMEM147-AS1 siRNA and its kinase activity using VX-680, showing more significant effect than the use of TMEM147-AS1 siRNA or VX-680 alone, which provides a potential strategy for EOC treatment.

FHL5 Controls Vascular Disease-Associated Gene Programs in Smooth Muscle Cells

BACKGROUND

Genome-wide association studies have identified hundreds of loci associated with common vascular diseases, such as coronary artery disease, myocardial infarction, and hypertension. However, the lack of mechanistic insights for many GWAS loci limits their translation into the clinic. Among these loci with unknown functions is UFL1-four-and-a-half LIM (LIN-11, Isl-1, MEC-3) domain 5 (FHL5; chr6q16.1), which reached genome-wide significance in a recent coronary artery disease/ myocardial infarction GWAS meta-analysis. UFL1-FHL5 is also associated with several vascular diseases, consistent with the widespread pleiotropy observed for GWAS loci.

METHODS

We apply a multimodal approach leveraging statistical fine-mapping, epigenomic profiling, and ex vivo analysis of human coronary artery tissues to implicate FHL5 as the top candidate causal gene. We unravel the molecular mechanisms of the cross-phenotype genetic associations through in vitro functional analyses and epigenomic profiling experiments in coronary artery smooth muscle cells.

RESULTS

We prioritized FHL5 as the top candidate causal gene at the UFL1-FHL5 locus through expression quantitative trait locus colocalization methods. FHL5 gene expression was enriched in the smooth muscle cells and pericyte population in human artery tissues with coexpression network analyses supporting a functional role in regulating smooth muscle cell contraction. Unexpectedly, under procalcifying conditions, FHL5 overexpression promoted vascular calcification and dysregulated processes related to extracellular matrix organization and calcium handling. Lastly, by mapping FHL5 binding sites and inferring FHL5 target gene function using artery tissue gene regulatory network analyses, we highlight regulatory interactions between FHL5 and downstream coronary artery disease/myocardial infarction loci, such as FOXL1 and FN1 that have roles in vascular remodeling.

CONCLUSIONS

Taken together, these studies provide mechanistic insights into the pleiotropic genetic associations of UFL1-FHL5. We show that FHL5 mediates vascular disease risk through transcriptional regulation of downstream vascular remodeling gene programs. These transacting mechanisms may explain a portion of the heritable risk for complex vascular diseases.

Silencing FHL2 inhibits bleomycin-induced pulmonary fibrosis through the TGF-β1/Smad signaling pathway

OBJECTIVE

This study aimed to investigate the inhibiting effects of FHL2 and Arbutin on cell fibrosis and their possible mechanisms.

METHODS

The mRNA expression of FHL2 in pulmonary fibrosis tissues was analyzed by bioinformatics. TGF⁃β1 induced fibrosis of mouse lung fibroblast (Mlg) and mouse primary pulmonary fibroblast (PPF) in rat's lung fibroblasts. FHL2 siRNA was transfected into Mlg and mouse PPF cells to inhibit FHL2. FHL2, α-smooth muscle actin (α-SMA), collagen 1 (Col I), and Fibronectin (Fn) were detected by qRT-PCR. Western blot expression levels of Smad3, p-Smad3, Smad2, and p-Smad2 proteins in cells. High-throughput drug screening for FHL2 inhibitors and the inhibitory effect of Arbutin on pulmonary fibrosis were validated in cellular and animal models of pulmonary fibrosis.

RESULTS

The mRNA expression of FHL2 in lung fiber tissue was increased. Meanwhile, the decrease of FHL2 expression significantly inhibited the cellular fibrosis morphological changes of rat's lung fibroblasts (Mlgs) and primary lung fibroblasts (PPFs). The expression levels of α⁃SMA, Col I, and Fn were decreased. High-throughput screening showed that Arbutin targeted FHL2. Arbutin alleviated bleomycin (BLM)-induced pulmonary fibrosis in rats by inhibiting FHL2 and then the TGF-β1/Smad signaling pathway.

CONCLUSION

Inhibition of FHL2 can effectively reduce the fibrosis process induced by TGF⁃β1 and bleomycin, and then inhibit the fibrosis.

Retrotransposon insertions associated with risk of neurologic and psychiatric diseases

Transposable elements (TEs) are active in neuronal cells raising the question whether TE insertions contribute to risk of neuropsychiatric disease. While genome-wide association studies (GWAS) serve as a tool to discover genetic loci associated with neuropsychiatric diseases, unfortunately GWAS do not directly detect structural variants such as TEs. To examine the role of TEs in psychiatric and neurologic disease, we evaluated 17,000 polymorphic TEs and find 76 are in linkage disequilibrium with disease haplotypes (P < 10-6 ) defined by GWAS. From these 76 polymorphic TEs, we identify potentially causal candidates based on having insertions in genomic regions of regulatory chromatin and on having associations with altered gene expression in brain tissues. We show that lead candidate insertions have regulatory effects on gene expression in human neural stem cells altering the activity of a minimal promoter. Taken together, we identify 10 polymorphic TE insertions that are potential candidates on par with other variants for having a causal role in neurologic and psychiatric disorders.

FHL3 promotes the formation of fast glycolytic muscle fibers by interacting with YY1 and muscle glycolytic metabolism

The proportions of the various muscle fiber types are important in the regulation of skeletal muscle metabolism, as well as animal meat production. Four-and-a-half LIM domain protein 3 (FHL3) is highly expressed in fast glycolytic muscle fibers and differentially regulates the expression of myosin heavy chain (MyHC) isoforms at the cellular level. Whether FHL3 regulates the transformation of muscle fiber types in vivo and the regulatory mechanism is unclear. In this study, muscle-specific FHL3 transgenic mice were generated by random integration, and lentivirus-mediated gene knockdown or overexpression in muscles of mice or pigs was conducted. Functional analysis showed that overexpression of FHL3 in muscles significantly increased the proportion of fast-twitch myofibers and muscle mass but decreased muscle succinate dehydrogenase (SDH) activity and whole-body oxygen consumption. Lentivirus-mediated FHL3 knockdown in muscles significantly decreased muscle mass and the proportion of fast-twitch myofibers. Mechanistically, FHL3 directly interacted with the Yin yang 1 (YY1) DNA-binding domain, repressed the binding of YY1 to the fast glycolytic MyHC2b gene regulatory region, and thereby promoted MyHC2b expression. FHL3 also competed with EZH2 to bind the repression domain of YY1 and reduced H3K27me3 enrichment in the MyHC2b regulatory region. Moreover, FHL3 overexpression reduced glucose tolerance by affecting muscle glycolytic metabolism, and its mRNA expression in muscle was positively associated with hemoglobin A1c (HbA1c) in patients with type 2 diabetes. Therefore, FHL3 is a novel potential target gene for the treatment of muscle metabolism-related diseases and improvement of animal meat production.

CMYA5 is a novel interaction partner of FHL2 in cardiac myocytes

Four-and-a-half LIM domains protein 2 (FHL2) is an anti-hypertrophic adaptor protein that regulates cardiac myocyte signalling and function. Herein, we identified cardiomyopathy-associated 5 (CMYA5) as a novel FHL2 interaction partner in cardiac myocytes. In vitro pull-down assays demonstrated interaction between FHL2 and the N- and C-terminal regions of CMYA5. The interaction was verified in adult cardiac myocytes by proximity ligation assays. Immunofluorescence and confocal microscopy demonstrated co-localisation in the same subcellular compartment. The binding interface between FHL2 and CMYA5 was mapped by peptide arrays. Exposure of neonatal rat ventricular myocytes to a CMYA5 peptide covering one of the FHL2 interaction sites led to an increase in cell area at baseline, but a blunted response to chronic phenylephrine treatment. In contrast to wild-type hearts, loss or reduced FHL2 expression in Fhl2-targeted knockout mouse hearts or in a humanised mouse model of hypertrophic cardiomyopathy led to redistribution of CMYA5 into the perinuclear and intercalated disc region. Taken together, our results indicate a direct interaction of the two adaptor proteins FHL2 and CMYA5 in cardiac myocytes, which might impact subcellular compartmentation of CMYA5.

The Roles of FHL3 in Cancer

The four and a half LIM domain protein 3, also named the LIM-protein FHL3, belongs to the LIM-only family. Based on the special structure of LIM-only proteins, FHL3 can perform significant functions in muscle proliferation and cardiovascular diseases by regulating cell growth and signal transduction. In recent years, there has been increasing evidence of a relation between FHLs and tumor biology, since FHL3 is often overexpressed or downregulated in different cancers. On the one hand, FHL3 can function as a tumor suppressor and influence the expression of downstream genes. On the other hand, FHL3 can also play a role as an oncoprotein in some cancers to promote tumor progression via phosphorylation. Thus, FHL3 is proposed to have a dual effect on cancer progression, reflecting its complex roles in cancer. This review focuses on the roles of FHL3 in cancer progression and discusses the interaction of FHL3 with other proteins and transcription factors. Finally, the clinical significance of FHL3 for the treatment of cancers is discussed.

Chemerin Impact on Alternative mRNA Transcription in the Porcine Luteal Cells

Chemerin participates in the regulation of processes related to physiological and disorder mechanisms in mammals, including metabolism, obesity, inflammation, and reproduction. In this study, we have investigated chemerin influence on alternative mRNA transcription within the porcine luteal cell transcriptome, such as differential expression of long non-coding RNAs (DELs) and their interactions with differentially expressed genes (DEGs), differences in alternative splicing of transcripts (DASs), and allele-specific expression (ASEs) related to the single nucleotide variants (SNVs) frequency. Luteal cells were collected from gilts during the mid-luteal phase of the oestrous cycle. After in vitro culture of cells un-/treated with chemerin, the total RNA was isolated and sequenced using the high-throughput method. The in silico analyses revealed 24 DELs cis interacting with 6 DEGs and trans-correlated with 300 DEGs, 137 DASs events, and 18 ASEs. The results enabled us to analyse metabolic and signalling pathways in detail, providing new insights into the effects of chemerin on the corpus luteum functions related to inflammatory response, leukocyte infiltration, the occurrence of luteotropic and luteolytic signals (leading to apoptosis and/or necroptosis). Validation of the results using qPCR confirmed the predicted expression changes. Chemerin at physiological concentrations significantly modifies the transcription processes in the porcine luteal cells.

Dynamic Expression and Chromatin Incorporation of ACT and CREM Transcription Factors in Testis Tissues of Infertile Men

OBJECTIVE

Activator of CREM in the testis (ACT) is a tissue specific transcription factor which activates cAMP responsive element modulator (CREM), a key transcription factor in differentiation of round spermatids into mature spermatozoa. They bind to CRE region in the promoters of transition protein genes (TNP1, TNP2) and protamine genes (PRM1 and PRM2), which are essential for sperm chromatin compaction, and regulates their transcription. This study was conducted to consider the expression of ACT and CREM and their regulatory roles on the expression of PRM1, PRM2, TNP1 and TNP2 genes in testis tissues of infertile men.

MATERIALS AND METHODS

In this case-control study, testicular biopsies were collected from 40 infertile men and classified into three groups: obstructive azoospermia (OA, n=10, positive control), round spermatid maturation arrest (SMA, n=20), Sertoli cell-only syndrome (SCOS, n=10, negative control group). Using quantitative real-time polymerase chain reaction (PCR), the expression profile of ACT, CREM, TNP1, TNP2, PRM1 and PRM2 genes were assessed in testicular samples and incorporation of ACT and CREM proteins on the promoters of PRM1, PRM2, TNP1 and TNP2 genes were also evaluated by ChIP-real time PCR.

RESULTS

Our results demonstrated significant decrease in the expression levels of ACT, CREM and in their incorporations on their target genes in SMA group in comparison to control groups (P≤0.05).

CONCLUSION

These data confirm that there is low expression and incorporation of ACT and CREM and of their target genes in infertilities which are associated with post-meiotic arrest.

The titin N2B and N2A regions: biomechanical and metabolic signaling hubs in cross-striated muscles

Muscle specific signaling has been shown to originate from myofilaments and their associated cellular structures, including the sarcomeres, costameres or the cardiac intercalated disc. Two signaling hubs that play important biomechanical roles for cardiac and/or skeletal muscle physiology are the N2B and N2A regions in the giant protein titin. Prominent proteins associated with these regions in titin are chaperones Hsp90 and αB-crystallin, members of the four-and-a-half LIM (FHL) and muscle ankyrin repeat protein (Ankrd) families, as well as thin filament-associated proteins, such as myopalladin. This review highlights biological roles and properties of the titin N2B and N2A regions in health and disease. Special emphasis is placed on functions of Ankrd and FHL proteins as mechanosensors that modulate muscle-specific signaling and muscle growth. This region of the sarcomere also emerged as a hotspot for the modulation of passive muscle mechanics through altered titin phosphorylation and splicing, as well as tethering mechanisms that link titin to the thin filament system.

Four-and-a-half LIM domain protein 2 (FHL2) deficiency protects mice from diet-induced obesity and high FHL2 expression marks human obesity

OBJECTIVE

Four-and-a-Half-LIM-domain-protein 2 (FHL2) modulates multiple signal transduction pathways but has not been implicated in obesity or energy metabolism. In humans, methylation and expression of the FHL2 gene increases with age, and high FHL2 expression is associated with increased body weight in humans and mice. This led us to hypothesize that FHL2 is a determinant of diet-induced obesity.

METHODS

FHL2-deficient (FHL2-/-) and wild type male mice were fed a high-fat diet. Metabolic phenotyping of these mice, as well as transcriptional analysis of key metabolic tissues was performed. Correlation of the expression of FHL2 and relevant genes was assessed in datasets from white adipose tissue of individuals with and without obesity.

RESULTS

FHL2 Deficiency protects mice from high-fat diet-induced weight gain, whereas glucose handling is normal. We observed enhanced energy expenditure, which may be explained by a combination of changes in multiple tissues; mild activation of brown adipose tissue with increased fatty acid uptake, increased cardiac glucose uptake and browning of white adipose tissue. Corroborating our findings in mice, expression of FHL2 in human white adipose tissue positively correlates with obesity and negatively with expression of browning-associated genes.

CONCLUSION

Our results position FHL2 as a novel regulator of obesity and energy expenditure in mice and human. Given that FHL2 expression increases during aging, we now show that low FHL2 expression associates with a healthy metabolic state.

Screening and identification of a novel FHL2 mutation by whole exome sequencing in twins with familial Waldenström macroglobulinemia

BACKGROUND

Waldenström macroglobulinemia (WM) is a rare chronic B-cell lymphoma. Familial clustering of WM has been observed over the years. However, little is known about the contribution of inherited genetic variants to familial WM cases.

METHODS

The authors performed whole exome sequencing (WES) of germline DNA samples from twins, one diagnosed with WM and the other diagnosed with immunoglobulin M monoclonal gammopathy of undetermined significance, and their healthy siblings. Bioinformatics analysis of public biological databases was used to identify the most relevant familial WM candidate from WES. Transcript expression and protein levels of the familial WM candidate were evaluated in the WM patient and 2 unaffected members of the kindred.

RESULTS

Among the 10 shared candidate mutations in the twins, the authors identified a novel heterozygous germline mutation in four and a half LIM domains protein 2 (FHL2; c.G226A, p.V76M) as a familial WM-associated mutation. FHL2 appeared to be connected with reported signaling pathways and disease-driving genes such as IL6 and HCK in WM. In addition, the authors found reduced FHL2 messenger RNA and protein expression in peripheral blood samples from the patient with WM in comparison with the healthy siblings.

CONCLUSIONS

Taken together, these findings indicate that an FHL2^g226a mutation may play an important role in familial WM, and they provide new screening possibilities for familial cases.

LAY SUMMARY

Familial clustering in Waldenström macroglobulinemia (WM) has been observed over the years. The authors performed whole exome sequencing of germline DNA samples from twins, one diagnosed with WM and the other diagnosed with immunoglobulin M monoclonal gammopathy of undetermined significance, and their healthy siblings. Among the 10 shared candidate mutations in the twins, a novel heterozygous germline mutation in four and a half LIM domains protein 2 (FHL2; c.G226A, p.V76M) was identified as the most relevant familial WM candidate through bioinformatics analysis of a public database. Also, messenger RNA and protein expression of FHL2 was significantly lower in peripheral blood mononuclear cells of the WM patient in comparison with the healthy siblings, and this suggested that the function of FHL2 was impaired when mutated.

The novel six LIM and one PET domain-containing protein Lmpt is involved in the immune response through activation of the NF-κB signalling pathway in the crustacean, Macrobrachium nipponense

The four-and-a-half LIM-only protein family of transcription co-factors participates in various cellular processes, such as cell proliferation, cell differentiation, apoptosis, cell adhesion, migration, transcription and signal transduction. However, the knowledge of the structural characteristics and immune functions of its ancestor Lmpt, which contains six LIM domains at the C-terminus and a PET domain at the N-terminus, is limited in invertebrates, especially in crustaceans. In the present study, a novel Lmpt from oriental river prawn (Macrobrachium nipponense) was identified, and its role in the immune response was investigated. Its full-length cDNA sequence was 6407 bp, which contained a 2595 bp ORF encoding 865 amino acids, exhibiting high similarity to the structure of Lmpt derived from other invertebrates. Tissue distribution analysis revealed that MnLmpt was widely expressed in all examined tissues, and high expression levels were observed in muscle, heart and intestine in M. nipponense. After experimental challenges with bacteria and virus, the transcription levels of MnLmpt significantly fluctuated in gill and hepatopancreas, indicating that it might play a role in the innate immune response in M. nipponense. Silencing of MnLmpt by dsRNA injection in vivo could promote bacterial growth, suggesting that MnLmpt exerted an antibacterial immune function in prawn. Immunocytochemistry assay results demonstrated that MnLmpt was able to translocate from the cytoplasm to the nucleus after being stimulated with pathogens. The expression levels of NF-κB signalling cascade members, such as dorsal, relish, TAK1, TAB1, Ikkβ, and Ikkε, and AMPs, including ALF4, Cru1, and Cru2, exhibited significant downregulation in the MnLmpt silenced group. Similarly, dual-luciferase reporter assays also demonstrated that MnLmpt could stimulate an NF-κB signalling cascade. Meanwhile, all of the LIM domains of MnLmpt could trigger NF-κB signalling; however, their cumulative effect on NF-κB promoter activation was hardly observed. These results showed that MnLmpt might play a crucial role in the innate immune response in M. nipponense, and these findings paved the way for a better understanding of the immune system in crustacean species.

Mechanosensing through Direct Binding of Tensed F-Actin by LIM Domains

Mechanical signals transmitted through the cytoplasmic actin cytoskeleton must be relayed to the nucleus to control gene expression. LIM domains are protein-protein interaction modules found in cytoskeletal proteins and transcriptional regulators. Here, we identify three LIM protein families (zyxin, paxillin, and FHL) whose members preferentially localize to the actin cytoskeleton in mechanically stimulated cells through their tandem LIM domains. A minimal actin-myosin reconstitution system reveals that representatives of all three families directly bind F-actin only in the presence of mechanical force. Point mutations at a site conserved in each LIM domain of these proteins disrupt tensed F-actin binding in vitro and cytoskeletal localization in cells, demonstrating a common, avidity-based mechanism. Finally, we find that binding to tensed F-actin in the cytoplasm excludes the cancer-associated transcriptional co-activator FHL2 from the nucleus in stiff microenvironments. This establishes direct force-activated F-actin binding as a mechanosensing mechanism by which cytoskeletal tension can govern nuclear localization.

Four and a half LIM domains protein 1 can be as a double-edged sword in cancer progression

Four and a half LIM domains protein 1 (FHL1), as the name suggests, contains four and a half LIM domains capable of interacting with various molecules, including structural proteins, kinases, and transcriptional machinery. FHL1 contains a zinc-finger domain and performs diverse roles in regulation of gene transcription, cytoarchitecture, cell proliferation, and signal transduction. Several studies have validated the importance of FHL1 in muscle development, myopathy, and cardiovascular diseases. Mutations in the FHL1 gene are associated with various myopathies. Recently, FHL1 was identified as a major host factor for chikungunya virus (CHIKV) infection in both humans and mice. Based on more recent findings over the last decade, FHL1 is proposed to play a dual role in cancer progression. On the one hand, FHL1 expression is suppressed in several cancer types, which correlates with increased metastatic disease and decreased survival. Moreover, FHL1 is reported to inhibit tumor cell growth and migration by associating with diverse signals, such as TGF-β and ER, and therefore considered a tumor suppressor. On the other hand, FHL1 can function as an oncogenic protein that promotes tumor progression upon phosphorylation, reflecting complex roles in cancer. This review primarily focuses on the dual role and underlying mechanisms of action of FHL1 in human cancer progression and its clinical relevance.

Up-regulated FHL2 inhibits ovulation through interacting with androgen receptor and ERK1/2 in polycystic ovary syndrome

BACKGROUND

The ovulatory dysfunction mechanisms underlying polycystic ovary syndrome (PCOS) are not completely understood. There is no effective therapy for PCOS so far.

METHODS

We measured the expression of four and a half LIM domain 2 (FHL2) and other related-genes in human granulosa cells (hGCs) from patients with and without PCOS. To minimise the heterogeneity of patients with PCOS, we only included PCOS patients meeting all three criteria according to the revised Rotterdam consensus. The in vitro effects of FHL2 on ovulatory genes and the underlying mechanisms were examined in KGN cells. The role of FHL2 in ovulation was investigated in vivo by overexpressing FHL2 in rat ovaries via intrabursal lentivirus injection.

FINDINGS

Increased FHL2 and androgen receptor (AR) expression and decreased CCAAT/enhancer-binding protein β (C/EBPβ) expression were observed in hGCs from patients with PCOS. FHL2 inhibited the expression of ovulation-related genes, including phosphorylated ERK1/2, C/EBPβ, COX2 and HAS2 in KGN cells. It was partially by interacting with AR to act as its co-regulator to inhibit C/EBPβ expression and by binding to ERK1/2 to inhibit its phosphorylation. Moreover, FHL2 abundance in hGCs was positively correlated with the basal serum testosterone concentration of patients with PCOS, and dihydrotestosterone (DHT)-induced FHL2 upregulation was mediated by AR signalling in KGN cells. Additionally, lentiviral-mediated functional FHL2 overexpression in rat ovaries for 1 week contributed to an impaired superovulatory response, displaying decreased numbers of retrieved oocytes and a lower MII oocyte rate. 3-week FHL2 overexpression rat models without superovulation led to acyclicity and polycystic ovary morphology.

INTERPRETATION

Our findings provide novel insights into the mechanisms underlying the pathogenesis of PCOS, suggesting that FHL2 could be a potential treatment target for ovulatory obstacles in PCOS. FUND: National Key Research and Development Program of China, National Natural Science Foundation, National Institutes of Health project and Shanghai Commission of Science and Technology.

Feedback inhibition of cAMP effector signaling by a chaperone-assisted ubiquitin system

Activation of G-protein coupled receptors elevates cAMP levels promoting dissociation of protein kinase A (PKA) holoenzymes and release of catalytic subunits (PKAc). This results in PKAc-mediated phosphorylation of compartmentalized substrates that control central aspects of cell physiology. The mechanism of PKAc activation and signaling have been largely characterized. However, the modes of PKAc inactivation by regulated proteolysis were unknown. Here, we identify a regulatory mechanism that precisely tunes PKAc stability and downstream signaling. Following agonist stimulation, the recruitment of the chaperone-bound E3 ligase CHIP promotes ubiquitylation and proteolysis of PKAc, thus attenuating cAMP signaling. Genetic inactivation of CHIP or pharmacological inhibition of HSP70 enhances PKAc signaling and sustains hippocampal long-term potentiation. Interestingly, primary fibroblasts from autosomal recessive spinocerebellar ataxia 16 (SCAR16) patients carrying germline inactivating mutations of CHIP show a dramatic dysregulation of PKA signaling. This suggests the existence of a negative feedback mechanism for restricting hormonally controlled PKA activities.

Role of Zebrafish fhl1A in Satellite Cell and Skeletal Muscle Development

Background:

Four-and-a-half LIM domains protein 1 (FHL1) mutations are associated with human myopathies. However, the function of this protein in skeletal development remains unclear.

Methods:

Whole-mount in situ hybridization and embryo immunostaining were performed.

Results:

Zebrafish Fhl1A is the homologue of human FHL1. We showed that fhl1A knockdown causes defective skeletal muscle development, while injection with fhl1A mRNA largely recovered the muscle development in these fhl1A morphants. We also demonstrated that fhl1A knockdown decreases the number of satellite cells. This decrease in satellite cells and the emergence of skeletal muscle abnormalities were associated with alterations in the gene expression of myoD, pax7, mef2ca and skMLCK. We also demonstrated that fhl1A expression and retinoic acid (RA) signalling caused similar skeletal muscle development phenotypes. Moreover, when treated with exogenous RA, endogenous fhl1A expression in skeletal muscles was robust. When treated with DEAB, an RA signalling inhibitor which inhibits the activity of retinaldehyde dehydrogenase, fhl1A was downregulated.

Conclusion:

fhl1A functions as an activator in regulating the number of satellite cells and in skeletal muscle development. The role of fhl1A in skeletal myogenesis is regulated by RA signaling.

FHL3 negatively regulates the differentiation of skeletal muscle satellite cells in chicken

As a member of four and a half LIM domain proteins, FHL3 gene-encoded protein (FHL3) plays an important role in skeletal muscle development and contraction. In this study, we determined the potential role of FHL3 in the proliferation and differentiation of primary satellite cells in chicken. RT-qPCR results showed that FHL3 mRNA was highly expressed in skeletal muscle in 12 chicken tissues. Four cell proliferation assays (CCK8 assay; EDU staining assay; flow cytometric detection of cell cycle assay; and detection of cell proliferation marker genes Ki67 and N-Ras assay) revealed that FHL3 knockdown had no effect on the proliferation rate of chicken satellite cells. FHL3 knockdown promoted the differentiation of satellite cells into myotubes, as evidenced by increased fusion index, number of nuclei per myotube, Myog, Myh7, Myf5, and Mrf4 mRNA expressions, and myog and myosin heavy chain protein expressions of myogenic markers (P < 0.05). These results showed that the FHL3 was a negative regulator of the differentiation and fusion of chicken satellite cells into myotubes. However, FHL3 expression was increased during the differentiation of chicken satellite cells into myotubes. The study suggested that FHL3 might have different functions in chicken myotubes compared with that in chicken satellite cells.

The LIM-Only Protein FHL2 is involved in Autophagy to Regulate the Development of Skeletal Muscle Cell

Scope: Four and a half LIM domain protein 2 (FHL2) is a LIM domain protein expressed in muscle tissue whose deletion is causative of myopathies. Although FHL2 has a confirmed important role in muscle development, its autophagy-related function in muscle differentiation has not been fully determined. Methods: C2C12 cells were treated with FHL2-konwdown or FHL2-overexpression. The morphology of C2C12 cells was observed by transmission electron microscopy. The mRNA and protein abundances of muscle related genes and autophagy related genes were measured by RT-PCR and western blot. Immunofluorescence and co-immunoprecipitation assay were used to verify the interaction between FHL2 and LC3 protein. Results: FHL2 silencing reduced LC3-Ⅱ protein expression and the amount of LC3 that co-immunoprecipitated with FHL2, indicating that FHL2 interacts with LC3-Ⅱ in the formation of autophagosomes. Moreover, the expression of muscle development marker genes such as MyoD1 and MyoG was lower in FHL2-silenced C2C12 cells but not in FHL2-overexpressing C2C12 cells. Electron microscopy analysis revealed large empty autophagosomes in FHL2-silenced myoblasts, while flow cytometry suggested that FHL2 silencing made cells more vulnerable to staurosporine-induced cell death. Conclusion: These results suggest that FHL2 interacts with LC3-Ⅱ in autophagosome formation to regulate the development of muscle cells.

Human CATSPER1 Promoter Is Regulated by CREB1 and CREMτ Transcriptional Factors In Vitro

BACKGROUND

The CATSPER1 gene encodes a CATSPER channel protein that selectively permeates Ca²⁺ ions, and CATSPER expression in sperm is essential for flagellum hyperactivation and, thus, male fertility. Little is known regarding the transcriptional regulation of CATSPER1, but previous studies have performed in silico analyses of transcription factor binding sites, including three CRE sites designated 0-2, in which CRE0 is located near the transcription start site.

OBJETIVES

We investigate if overexpression of CREB-A and CREMτ transcription factors might regulate CATSPER1 expression.

MATERIAL AND METHODS

In this study, the transcriptional regulation of the CATSPER1 gene by CREB-A and CREMτ transcriptions factors was determined by dual-luciferase assays in HEK293 and GC1-spg cells, and important CRE sites were mutated and analyzed for transcriptional regulation.

RESULTS

The deletion of the CRE1 site dramatically increased the transcriptional activity of the CATSPER1 promoter in HEK293 and GC1-spg cells. In HEK293 cells, the CREB-A transcription factor positively regulated CATSPER1 gene expression, while the presence of CREB-A and CREMτ factors synergistically enhanced promoter activity in these cells. In contrast, deletion of CRE0 prevented any transcriptional activity of the CATSPER1 promoter in GC1-spg spermatogonial cells, but expression of either CREB-A or CREMτ restored such transcriptional activity.

CONCLUSIONS

The human CATSPER1 promoter is positively regulated in vitro by CREB-A in HEK293 and GC1-spg cells. Both lines showed differential transcriptional regulation, which was defined by the factors and coactivators present in each cell line as well as the context in which the CRE sites were found in the promoter.

Differentially Methylated Genes in Saliva are linked to Childhood Stress

Chronic and severe stress exposure in early childhood is associated with the development of psychiatric disorders. Yet, the molecular mechanisms underlying this relationship remain poorly understood. Here, we profile molecular marks (DNA methylation and gene expression) throughout the human genome to determine the associations between childhood stress exposure and gene regulation. To do so, we collected saliva tissue from prepubertal girls (mean age 10.9 ± 1.26 years) who had experienced different levels of childhood adversity, ranging from mild to severe. We found 122 differentially methylated genes (FDR P-value < 0.05) associated with high childhood stress exposures that affect brain development. Of these differentially methylated genes, 12 also differed in gene expression. To further investigate the potential effects of stress exposure on gene regulation, we examined the DNA sequences flanking all the differentially methylated loci. This analysis revealed enrichment of known binding sites for transcription factors, suggesting that DNA methylation may regulate gene expression by mediating transcription factor binding on these genes. Together, these findings indicate a possible neuromolecular mechanism linking children’s social experiences with risk for anxiety and depressive disorders.

FHL3 links cell growth and self-renewal by modulating SOX4 in glioma

Differentiation status significantly affects the properties of malignant glioma cells, with non-stem cells inducing tumor enlargement and stem-like cells driving tumor initiation and treatment resistance. It is not completely understood how the same protein can have a distinct role in these cell populations. Here, we report that four and a half LIM domain protein 3 (FHL3) has an inhibitory effect on proliferation in non-stem glioma cells and a non-proliferative effect in glioma stem cells (GSCs). In GSCs, we show that FHL3 interacts with the Smad2/3 protein complex at the SOX4 promoter region, inhibits SOX4 transcriptional activity by recruiting PPM1A phosphatase to Smad2/3, and then suppresses GSC tumor sphere formation and self-renewal in vitro and in vivo via downregulation of SOX2 expression. Altogether, these findings highlight the role of FHL3 as a stemness-suppressor in regulation of the Smad2/3-SOX4-SOX2 axis in glioma.

Increased expression of FHL2 promotes tumorigenesis in cervical cancer and is correlated with poor prognosis

PURPOSE

Increasing evidence demonstrates that the four and a half LIM domain (FHL) gene and its protein products have different functions in the progression of various malignancies. However, the role of FHL protein 2 (FHL2) in cervical cancer (CC) has not been fully elucidated. In this study, we investigated the prognostic value of FHL2 expression in human CC tissues and the potential molecular mechanisms through which FHL2 modulates CC cell proliferation and apoptosis.

MATERIALS AND METHODS

We measured FHL2 expression in CC cell lines and tissues by quantitative real-time polymerase chain reaction and Western blot assays. The effects of FHL2 knockdown on cell proliferation and apoptosis in two CC cell lines were examined using RNA interference, cell counting kit-8, Western blot and flow cytometry assays. Furthermore, we assessed phosphorylated protein kinase B (p-AKT) and phosphorylated mammalian target of rapamycin (p-mTOR) expression in two CC cell lines to determine whether the AKT/mTOR pathway is involved in the effects of FHL2 silencing on cell proliferation and apoptosis. Nude mice tumorigenicity experiments were also performed to evaluate the effects of FHL2 on HeLa cell growth in vivo.

RESULTS

We found that FHL2 was significantly upregulated in CC cell lines and tissues. According to survival curves, high FHL2 expression levels in patients were correlated with poor prognosis. Moreover, by decreasing p-AKT and p-mTOR protein levels, silencing FHL2 significantly inhibited cell proliferation and induced apoptosis. FHL2 knockdown also induced apoptosis by increasing the Bax-to-Bcl2 ratio. By contrast, FHL2 overexpression significantly promoted cell proliferation. Finally, decreased tumour growth in an in vivo animal model also demonstrated the tumour-suppressing effects of FHL2 knockdown.

CONCLUSION

Our findings indicate that FHL2 is an important prognostic factor in CC and that it plays a crucial oncoprotein role by promoting cell proliferation and inhibiting apoptosis in CC, possibly by targeting the AKT/mTOR pathway.

Abnormal spermatogenesis following sodium fluoride exposure is associated with the downregulation of CREM and ACT in the mouse testis

cAMP response element modulator (CREM) is involved in regulating gene expression in normal spermatogenesis. The transcriptional activity of CREM is partly regulated by activator of CREM in the testis (ACT). To investigate the effects of different concentrations of sodium fluoride (NaF) on the gene and protein expression of CREM and ACT in the mouse testis, sexually mature male Kunming mice were exposed to 50, 100, or 150 mg/L NaF in their drinking water for 90 days. NaF reduced the sperm count and viability and increased the percentage of malformed sperm in a dose-dependent manner. The mRNA expression of CREM and ACT was markedly downregulated in the NaF-treated groups. Furthermore, immunohistochemistry revealed that CREM and ACT proteins were decreased significantly in the 50, 100, and 150 mg/L NaF-treated groups compared to the control group. These findings indicate that the decreased gene and protein expression of CREM and ACT in the testis is associated with an impairment of reproductive functions by NaF.

Unique Genes in Tumor-Positive Sentinel Lymph Nodes Associated with Nonsentinel Lymph Node Metastases in Melanoma

BACKGROUND

Current risk assessment tools to estimate the risk of nonsentinel lymph node metastases after completion lymphadenectomy for a positive sentinel lymph node (SLN) biopsy in cutaneous melanoma are based on clinical and pathologic factors. We identified a novel genetic signature that can predict non-SLN metastases in patients with cutaneous melanoma staged with a SLN biopsy.

METHODS

RNA was collected for tumor-positive SLNs in patients staged by SLN biopsy for cutaneous melanoma. All patients with a tumor-positive SLN biopsy underwent completion lymphadenectomy. A 1:10 case:control series of positive and negative non-SLN patients was analyzed by microarray and quantitative RT-PCR. Candidate differentially expressed genes were validated in a 1:3 case:control separate cohort of positive and negative non-SLN patients.

RESULTS

The 1:10 case:control discovery set consisted of 7 positive non-SLN cases matched to 70 negative non-SLN controls. The cases and controls were similar with regards to important clinicopathologic factors, such as gender, primary tumor site, age, ulceration, and thickness. Microarray and RT-PCR identified six potential differentially expressed genes for validation. In the 40-patient separate validation set, 10 positive non-SLN patients were matched to 30 negative non-SLN controls based on gender, ulceration, age, and thickness. Five of the six genes were differentially expressed. The five gene panel identified patients at low (7.1%) and high risk (66.7%) for non-SLN metastases.

CONCLUSIONS

A novel, non-SLN gene score based on differential expressed genes in a tumor-positive SLN can identify patients at high and low risk for non-SLN metastases.

A signature motif in LIM proteins mediates binding to checkpoint proteins and increases tumour radiosensitivity

Tumour radiotherapy resistance involves the cell cycle pathway. CDC25 phosphatases are key cell cycle regulators. However, how CDC25 activity is precisely controlled remains largely unknown. Here, we show that LIM domain-containing proteins, such as FHL1, increase inhibitory CDC25 phosphorylation by forming a complex with CHK2 and CDC25, and sequester CDC25 in the cytoplasm by forming another complex with 14-3-3 and CDC25, resulting in increased radioresistance in cancer cells. FHL1 expression, induced by ionizing irradiation in a SP1- and MLL1-dependent manner, positively correlates with radioresistance in cancer patients. We identify a cell-penetrating 11 amino-acid motif within LIM domains (eLIM) that is sufficient for binding CHK2 and CDC25, reducing the CHK2–CDC25 and CDC25–14-3-3 interaction and enhancing CDC25 activity and cancer radiosensitivity accompanied by mitotic catastrophe and apoptosis. Our results provide novel insight into molecular mechanisms underlying CDC25 activity regulation. LIM protein inhibition or use of eLIM may be new strategies for improving tumour radiosensitivity.

CDC25 phosphatases are important cell cycle regulators. Here, the authors show that the LIM domain-containing proteins (for example, FHL1) induce inhibitory CDC25 phosphorylation resulting in radioresistance and that a specific peptide can increase tumour radiosensitivity by increasing CDC25 activity.

Four-and-a-half LIM Domains 1 (FHL1) Protein Interacts with the Rho Guanine Nucleotide Exchange Factor PLEKHG2/FLJ00018 and Regulates Cell Morphogenesis

PLEKHG2/FLJ00018 is a Gβγ-dependent guanine nucleotide exchange factor for the small GTPases Rac and Cdc42 and has been shown to mediate the signaling pathways leading to actin cytoskeleton reorganization. Here we showed that the zinc finger domain-containing protein four-and-a-half LIM domains 1 (FHL1) acts as a novel interaction partner of PLEKHG2 by the yeast two-hybrid system. Among the isoforms of FHL1 (i.e. FHL1A, FHL1B, and FHL1C), FHL1A and FHL1B interacted with PLEKHG2. We found that there was an FHL1-binding region at amino acids 58-150 of PLEKHG2. The overexpression of FHL1A but not FHL1B enhanced the PLEKHG2-induced serum response element-dependent gene transcription. The co-expression of FHL1A and Gβγ synergistically enhanced the PLEKHG2-induced serum response element-dependent gene transcription. Increased transcription activity was decreased by FHL1A knock-out with the CRISPR/Cas9 system. Compared with PLEKHG2-expressing cells, the number and length of finger-like protrusions were increased in PLEKHG2-, Gβγ-, and FHL1A-expressing cells. Our results provide evidence that FHL1A interacts with PLEKHG2 and regulates cell morphological change through the activity of PLEKHG2.

Expression of the Transcriptional Coregulator FHL2 in Human Breast Cancer: A Clinicopathologic Study

OBJECTIVE

Although the Four and a Half LIM domain protein 2 (FHL2) has been suggested to play an important role in tumor development, this has not been investigated in breast cancer.

METHODS

Paraffin-embedded tissues from patients (n = 85) with primary breast cancer were submitted to immunohistochemical investigation of FHL2 expression and subsequent correlation with clinicopathologic parameters and patient survival.

RESULTS

The expression of FHL2 was confined to the cytoplasm of the tumor cells. Forty (47%) of 85 samples showed weak expression of FHL2, whereas high expression was found in 45 tumors (53%). A statistically significant positive correlation was observed between FHL2 and androgen receptor expression (P = .029). Patients with tumors expressing low amounts of FHL2 were characterized by a significantly better survival compared to those with high intratumoral FHL2 expression (P = .0215, log-rank test). The additional stratification according to adjuvant tamoxifen treatment revealed a significantly improved survival rate for patients receiving tamoxifen and being diagnosed with a tumor expressing high amounts of FHL2. This might indicate that tamoxifen is at least partially capable of reversing the negative prognostic impact of high FHL2 expression. Multivariate Cox regression analysis revealed FHL2 expression as a significant independent predictor of survival.

CONCLUSION

The specific expression in tumor tissue points to an important functional role of FHL2 in human breast cancer. Our survival data indicate that the expression of FHL2 in primary breast cancer is a potentially relevant prognostic factor. Further studies are warranted to elucidate whether analysis of FHL2 expression is suitable to predict response to antihormonal treatment with tamoxifen.

KLF8 promotes tumorigenesis, invasion and metastasis of colorectal cancer cells by transcriptional activation of FHL2

The transcription factor Krüppel-like factor (KLF)8 plays an important role in the formation of several human tumors, including colorectal cancer. We recently identified four-and-a-half LIM protein 2 (FHL2) as a critical inducer of the epithelial-to-mesenchymal transition (EMT) and invasion. However, the molecular mechanism by which KLF8 affects FHL2-mediated tumor proliferation, EMT and metastasis remains unknown. Here, we showed that KLF8 overexpression promoted EMT and metastatic phenotypes. KLF8 expression was stimulated by transforming growth factor (TGF)-β1. Moreover, KLF8 acted as a potential EMT inducer by stimulating vimentin expression and inducing a loss of E-cadherin in stable KLF8-transfected cells. KLF8 overexpression induced a strong increase in FHL2 expression, and a positive correlation between the expression patterns of KLF8 and FHL2 was observed in CRC cells. Promoter reporter and chromatin immunoprecipitation (ChIP) assays demonstrated that KLF8 directly bound to and activated the human FHL2 gene promoter. However, siRNA-mediated repression of FHL2 in KLF8-overexpressing cells reversed the EMT and the proliferative and metastatic phenotypes. In vivo, KLF8 promoted FHL2-mediated proliferation and metastasis via orthotopic implantation. Taken together, this work identified KLF8-induced FHL2 activation as a novel and critical signaling mechanism underlying human breast/colorectal cancer invasion and metastasis.

The four and a half LIM domains 2 (FHL2) regulates ovarian granulosa cell tumor progression via controlling AKT1 transcription

The four and a half LIM domains 2 (FHL2) has been shown to play important roles in the regulation of cell proliferation, survival, adhesion, motility and signal transduction in a cell type and tissue-dependent manner. However, the function of FHL2 in ovarian physiology and pathology is unclear. The aim of this study was to determine the role and functional mechanism of FHL2 in the progression of ovarian granulosa cell tumors (GCTs). Immunohistochemical analysis indicated that FHL2 was overexpressed in GCT tissues. Cellular localization of FHL2 in GCT cells was cell cycle dependent. Knockdown of FHL2 suppressed GCT cell growth, reduced cell viability and inhibited cell migration. Consistently, ectopic expression of FHL2 in GCT cells with very low endogenous FHL2 promoted cell growth, improved cell viability and enhance cell migration. Importantly, overexpression of FHL2 promoted GCT progression in vivo. Mechanistic studies indicated that FHL2 regulates AKT1 gene expression in vitro and in vivo. Knockdown of FHL2 or AKT1 in GCT cell lines induced very similar phenotypes. Ectopic expression of constitutively active AKT1 rescued FHL2 knockdown-induced arrest of GCT cell growth and reduction of GCT cell viability, suggesting that FHL2 regulates GCT cell growth and viability through controlling AKT1 expression. Finally, co-immunoprecipitation and chromatin immunoprecipitation analyses indicated that FHL2 functions as a co-activator of NFκB and AP-1 to regulate AKT1 gene transcription. In conclusion, results from the present study indicate that FHL2 exerts its oncogenic action in GCT cells via controlling AKT1 gene expression. FHL2 is a promising target for the development of novel drugs against ovarian granulosa cell tumor.

Calcitonin gene-related peptide induced migraine attacks in patients with and without familial aggregation of migraine

Background

Calcitonin gene-related peptide provokes migraine attacks in 65% of patients with migraine without aura. Whether aggregation of migraine in first-degree relatives (family load) or a high number of risk-conferring single nucleotide polymorphisms contributes to migraine susceptibility to calcitonin gene-related peptide infusion in migraine patients is unknown. We hypothesized that genetic enrichment plays a role in triggering of migraine and, therefore, migraine without aura patients with high family load would report more migraine attacks after calcitonin gene-related peptide infusion than patients with low family load.

Methods

We allocated 40 previously genotyped migraine without aura patients to receive intravenous infusion of 1.5 µg/min calcitonin gene-related peptide and recorded migraine attacks including headache characteristics and associated symptoms. Information of familial aggregation was obtained by telephone interview of first-degree relatives using a validated semi-structured questionnaire.

Results

Calcitonin gene-related peptide infusion induced a migraine-like attack in 75% (12 out of 16) of patients with high family load compared to 52% (12 out of 23) with low family load ( P = 0.150). In addition, we found that the migraine response after calcitonin gene-related peptide was not associated with specific or a high number of risk-conferring single nucleotide polymorphisms of migraine without aura.

Conclusion

We found no statistical association between familial aggregation of migraine and hypersensitivity to calcitonin gene-related peptide infusion in migraine without aura patients. We also demonstrated that the currently known single nucleotide polymorphisms conferring risk of migraine without aura have no additive effect on calcitonin gene-related peptide induced migraine-like attacks.

Plumbagin exhibits an anti-proliferative effect in human osteosarcoma cells by downregulating FHL2 and interfering with Wnt/β-catenin signalling

Plumbagin, a naphthoquinone constituent of Plumbago zeylanica L. (Plumbaginaceae) is widely used in traditional Chinese medicine as an antifungal, antibacterial and anti-inflammatory agent. Plumbagin is known to exhibit proapoptotic, antiangiogenic and antimetastatic effects in cancer cells. The transcriptional co-factor four and a half LIM domains 2 (FHL2) is a multifunctional adaptor protein that is involved in the regulation of gene expression, signal transduction and cell proliferation and differentiation, and also acts as a tumor suppressor or oncoprotein depending on the tissue microenvironment. The present study investigated the effect of plumbagin on FHL2 expression, Wnt/β-catenin signalling and its anti-proliferative activity in various human osteosarcoma cell lines, including SaOS2, MG63, HOS and U2OS. The cells were exposed to plumbagin and the expression of FHL2 was evaluated using western blot analysis. Furthermore, the anti-proliferative effect of plumbagin was evaluated using a 3-(4,5 dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. In addition, since FHL2 is involved in Wnt/β-catenin signaling, the effect of plumbagin on β-catenin and its primary target genes, including v-myc avian myelocytomatosis viral oncogene homolog (c-Myc) and WNT1 inducible signaling pathway protein-1 (WISP-1), was evaluated using western blot analysis. It was observed that plumbagin suppressed the expression of FHL2 and exhibited significant anti-proliferative activity in osteosarcoma cells. It also attenuated Wnt/β-catenin signalling by downregulating β-catenin and its target genes, including c-Myc and WISP-1. In conclusion, plumbagin demonstrated anti-proliferative activity in osteosarcoma cells by downregulating FHL2 and interfering with Wnt/β-catenin signalling.

Protein-protein interactions of the LIM-only protein FHL2 and functional implication of the interactions relevant in cardiovascular disease

FHL2 belongs to the LIM-domain only proteins and contains four and a half LIM domains, each of which are composed of two zinc finger structures. FHL2 exhibits specific interaction with proteins exhibiting diverse functions, including transmembrane receptors, transcription factors and transcription co-regulators, enzymes, and structural proteins. The function of these proteins is regulated by FHL2, which modulates intracellular signal transduction pathways involved in a plethora of cellular tasks. The present review summarizes the current knowledge on the protein interactome of FHL2 and provides an overview of the functional implication of these interactions in apoptosis, migration, and regulation of nuclear receptor function. FHL2 was originally identified in the heart and there is extensive literature available on the role of FHL2 in the cardiovascular system, which is also summarized in this review.

FHL3 differentially regulates the expression of MyHC isoforms through interactions with MyoD and pCREB

In skeletal muscle, muscle fiber types are defined by four adult myosin heavy chain (MyHC) isoforms. Four and a half LIM domain protein 3 (FHL3) regulates myoblasts differentiation and gene expression by acting as a transcriptional co-activator or co-repressor. However, how FHL3 regulates MyHC expression is currently not clear. In this study, we found that FHL3 down-regulated the expression of MyHC 1/slow and up-regulated the expression of MyHC 2a and MyHC 2b, whereas no significant effect was found on MyHC 2x expression. MyoD and phosphorylated cAMP response element binding protein (pCREB) played important roles in the regulation of MyHC 1/slow and MyHC 2a expression by FHL3, respectively. FHL3 could interact with MyoD, CREB and pCREB in vivo. pCREB had stronger interaction with the cyclic AMP-responsive elements (CRE) of the MyHC 2a promoter compared with CREB, and FHL3 significantly affected the binding capacity of pCREB to CRE. We established a model in which FHL3 promotes the expression of MyHC 2a through CREB-mediated transcription and inhibits the expression of MyHC 1/slow by inhibiting MyoD transcription activity during myogenesis. Our data support the notion that FHL3 plays important roles in the regulation of muscle fiber type composition.

The FHL2 regulation in the transcriptional circuitry of human cancers

The Four-and-a-half LIM (FHL)-only protein is a subfamily of protein members under the LIM-only protein family. These proteins are identified by their characteristic four and a half cysteinerich LIM homeodomain. Five members have been categorized into the FHL subfamily, which are FHL1, FHL2, FHL3, FHL4 and activator of CREM in testis (ACT) in human. FHL2 is amongst the most examined members within the family. Fhl2, the gene that code for the protein, is transcriptionally regulated by diverse types of transcription factors, for example, p53, serum response factor (SRF), and specificity protein 1 (Sp1). The expression of FHL2 is found in different tissues and organs and has been reported as a critical participant influencing the wide types of cancer such as breast cancer, gastrointestinal (GI) cancers, liver cancer and prostate cancer. The expression profile of FHL2 appeared to have a significant functional role in the carcinogenesis of these cancers which are mediated by different types of transcription factor including both tumor suppressors and inducers. In this review, we will first describe the molecular network governing FHL2 expression, which focus on the transcription factors conveying FHL2-initiated responses. In the second part, FHL2-linked cancers and the underlying molecular machinery will be discussed. Factors other than transcriptional regulation which may involve the cancer progression such as mutations of fhl2 and posttranslational modifications of the protein will also be mentioned.

Absence of Four-and-a-Half LIM Domain Protein 2 Decreases Atherosclerosis in ApoE −/− Mice

Objective—

Four-and-a-half LIM domain protein-2 (FHL2) is expressed in endothelial cells, vascular smooth muscle cells, and leukocytes. It regulates cell survival, migration, and inflammatory response, but its role in atherogenesis is unknown.

Approach and Results—

To investigate the role of FHL2 in atherosclerosis, FHL2-deficient mice were crossed with ApoE-deficient mice, to generate ApoE/FHL2−/− mice. After high-fat diet, ApoE/FHL2−/− mice had significantly smaller atherosclerotic plaques than ApoE−/− mice in the aortic sinus, the brachiocephalic artery, and the aorta. This was associated with enhanced collagen and smooth muscle cell contents and a 2-fold reduction in macrophage content within the plaques of ApoE/FHL-2−/− versus ApoE−/− mice. This could be explained, in part, by the reduction in aortic ICAM-1 (intracellular adhesion molecule) mRNA and VCAM-1 (vascular cell adhesion molecule) protein expression in the plaque. Aortic gene expression of the chemokines CX3CL1 and CCL5 was increased in ApoE/FHL2−/− versus ApoE−/− mice. Peritoneal thioglycollate injection elicited equivalent numbers of monocytes and macrophages in both groups, but a significantly lower number of proinflammatory Ly6C high monocytes were recruited in ApoE/FHL2−/− versus ApoE−/− mice. Furthermore, mRNA levels of CX3CR1 were 2-fold higher in monocytes from ApoE/FHL2−/− versus ApoE−/− mice. Finally, we investigated the potential importance of myeloid cell FHL2 deficiency in atherosclerosis. After being irradiated, ApoE−/− or ApoE/FHL2−/− mice were transplanted with ApoE−/− or ApoE/FHL2−/− bone marrow. After high-fat diet, both chimeric groups developed smaller plaques than ApoE−/− transplanted with ApoE−/− bone marrow.

Conclusions—

These results suggest that FHL2 in both myeloid and vascular cells may play an important role in atherosclerosis by promoting proinflammatory chemokine production, adhesion molecule expression, and proinflammatory monocyte recruitment.

Migraine pathophysiology: lessons from mouse models and human genetics

Migraine is a common, disabling, and undertreated episodic brain disorder that is more common in women than in men. Unbiased genome-wide association studies have identified 13 migraine-associated variants pointing at genes that cluster in pathways for glutamatergic neurotransmission, synaptic function, pain sensing, metalloproteinases, and the vasculature. The individual pathogenetic contribution of each gene variant is difficult to assess because of small effect sizes and complex interactions. Six genes with large effect sizes were identified in patients with rare monogenic migraine syndromes, in which hemiplegic migraine and non-hemiplegic migraine with or without aura are part of a wider clinical spectrum. Transgenic mouse models with human monogenic-migraine-syndrome gene mutations showed migraine-like features, increased glutamatergic neurotransmission, cerebral hyperexcitability, and enhanced susceptibility to cortical spreading depression, which is the electrophysiological correlate of aura and a putative trigger for migraine. Enhanced susceptibility to cortical spreading depression increased sensitivity to focal cerebral ischaemia, and blocking of cortical spreading depression improved stroke outcome in these mice. Changes in female hormone levels in these mice modulated cortical spreading depression susceptibility in much the same way that hormonal fluctuations affect migraine activity in patients. These findings confirm the multifactorial basis of migraine and might allow new prophylactic options to be developed, not only for migraine but potentially also for migraine-comorbid disorders such as epilepsy, depression, and stroke.

Identification of FHL2-regulated genes in liver by microarray and bioinformatics analysis

FHL2 is a LIM domain protein that is able to form various protein complexes and regulate gene transcription. Recent findings showed that FHL2 is a potential tumor suppressor gene that was down-regulated in hepatocellular carcinoma. In the present study, microarray profiling of gene expression was performed to identify the genes regulated by FHL2 in mouse livers. The differentially expressed genes were further analyzed by bioinformatics tools including DAVID, KEGG, and STRING. Our data illustrate that FHL2 affects genes involved in various functions including signal transduction, responses to external stimulus, cancer-related pathways, cardiovascular function and regulation of actin cytoskeleton. Moreover, a network of differentially expressed genes identified in this study and known FHL2-interacting proteins was constructed. Then, genes identified by bioinformatics tools and most functional relevant to FHL2 were selected for further validation. Finally, the differential expression of Ar, Id3, Inhbe, Alas1, Bcl6, Pparδ, Angptl4, and Erbb4 were confirmed by quantitative real-time PCR. In summary, we have established a database of genes that are potentially regulated by FHL2 and these genes should be future targets for the elucidation of functional roles of FHL2.

FHL2 regulates hematopoietic stem cell functions under stress conditions

FHL2, a member of the four and one half LIM domain protein family, is a critical transcriptional modulator. Here, we identify FHL2 as a critical regulator of hematopoietic stem cells (HSCs) that is essential for maintaining HSC self-renewal under regenerative stress. We find that Fhl2 loss has limited effects on hematopoiesis under homeostatic conditions. In contrast, Fhl2-null chimeric mice reconstituted with Fhl2-null bone marrow cells developed abnormal hematopoiesis with significantly reduced numbers of HSCs, hematopoietic progenitor cells (HPCs), red blood cells and platelets as well as hemoglobin levels. In addition, HSCs displayed a significantly reduced self-renewal capacity and were skewed toward myeloid lineage differentiation. We find that Fhl2 loss reduces both HSC quiescence and survival in response to regenerative stress, probably as a consequence of Fhl2-loss-mediated down-regulation of cyclin dependent kinase (CDK)-inhibitors, including p21(Cip) and p27(Kip1). Interestingly, FHL2 is regulated under control of a tissue specific promoter in hematopoietic cells and it is down-regulated by DNA hypermethylation in the leukemia cell line and primary leukemia cells. Furthermore, we find that down-regulation of FHL2 frequently occurs in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) patients, raising a possibility that FHL2 down-regulation plays a role in the pathogenesis of myeloid malignancies.

The LIM domain protein nTRIP6 recruits the mediator complex to AP-1-regulated promoters

Several LIM domain proteins regulate transcription. They are thought to act through their LIM protein-protein interaction domains as adaptors for the recruitment of transcriptional co-regulators. An intriguing example is nTRIP6, the nuclear isoform of the focal adhesion protein TRIP6. nTRIP6 interacts with AP-1 and enhances its transcriptional activity. nTRIP6 is also essential for the transrepression of AP-1 by the glucocorticoid receptor (GR), by mediating GR tethering to promoter-bound AP-1. Here we report on the molecular mechanism by which nTRIP6 exerts these effects. Both the LIM domains and the pre-LIM region of nTRIP6 are necessary for its co-activator function for AP-1. Discrete domains within the pre-LIM region mediate the dimerization of nTRIP6 at the promoter, which enables the recruitment of the Mediator complex subunits THRAP3 and Med1. This recruitment is blocked by GR, through a competition between GR and THRAP3 for the interaction with the LIM domains of nTRIP6. Thus, nTRIP6 both positively and negatively regulates transcription by orchestrating the recruitment of the Mediator complex to AP-1-regulated promoters.

Identification and characterization of MT-1X as a novel FHL3-binding partner

Four and a half LIM domain protein 3 (FHL3) is a member of the FHL protein family that plays roles in the regulation of cell survival, cell adhesion and signal transduction. However, the mechanism of action for FHL3 is not yet clear. The aim of present study was to identify novel binding partner of FHL3 and to explore the underlying mechanism. With the use of yeast two-hybrid screening system, FHL3 was used as the bait to screen human fetal hepatic cDNA library for interacting proteins. Methionine-1X was identified as a novel FHL3 binding partner. The interaction between FHL3 and the full length MT-1X was further confirmed by yeast two-hybrid assay, co-immunoprecipitation and GST pull-down assays. Furthermore,the result demonstrated that MT-1X knockdown promoted the FHL3-induced inhibitory effect on HepG2 cells by regulating FHL3-mediated Smad signaling and involving in the modulation the expression of G2/M phase-related proteins through interaction with FHL3. These findings suggest that functional interactions between FHL3 and MT-1X may provide some clues to the mechanisms of FHL3-regulated cell proliferation.

Four-and-a-half LIM domains proteins are novel regulators of the protein kinase D pathway in cardiac myocytes

PKD (protein kinase D) is a serine/threonine kinase implicated in multiple cardiac roles, including the phosphorylation of the class II HDAC5 (histone deacetylase isoform 5) and thereby de-repression of MEF2 (myocyte enhancer factor 2) transcription factor activity. In the present study we identify FHL1 (four-and-a-half LIM domains protein 1) and FHL2 as novel binding partners for PKD in cardiac myocytes. This was confirmed by pull-down assays using recombinant GST-fused proteins and heterologously or endogenously expressed PKD in adult rat ventricular myocytes or NRVMs (neonatal rat ventricular myocytes) respectively, and by co-immunoprecipitation of FHL1 and FHL2 with GFP–PKD1 fusion protein expressed in NRVMs. In vitro kinase assays showed that neither FHL1 nor FHL2 is a PKD1 substrate. Selective knockdown of FHL1 expression in NRVMs significantly inhibited PKD activation and HDAC5 phosphorylation in response to endothelin 1, but not to the α₁-adrenoceptor agonist phenylephrine. In contrast, selective knockdown of FHL2 expression caused a significant reduction in PKD activation and HDAC5 phosphorylation in response to both stimuli. Interestingly, neither intervention affected MEF2 activation by endothelin 1 or phenylephrine. We conclude that FHL1 and FHL2 are novel cardiac PKD partners, which differentially facilitate PKD activation and HDAC5 phosphorylation by distinct neurohormonal stimuli, but are unlikely to regulate MEF2-driven transcriptional reprogramming.

Protein kinase D has multiple roles in cardiac myocytes, where its regulatory mechanisms remain incompletely defined. In the present study we identify four-and-a-half LIM domains proteins 1 and 2 as novel binding partners and regulators of protein kinase D in this cell type.