Specific haplotypes of the CALPAIN-5 gene are associated with polycystic ovary syndrome

CAPN5 attenuates cigarette smoke extract-induced apoptosis and inflammation in BEAS-2B cells

INTRODUCTION

Apoptosis and chronic inflammation are the main phenotypes in chronic obstructive pulmonary disease (COPD) pathogenesis. Cigarette smoke exposure is the leading risk factor for COPD, which causes aberrant airway epithelial structure and function. As a non-classical calpain, the molecular function of calpain5 (CAPN5) in COPD remains unclear. This study investigated the role of CAPN5 in mediating cigarette smoke extract (CSE)-induced apoptosis and inflammation.

METHODS

Immunohistochemistry (IHC) and Western blotting (WB) were performed to detect the location and expression of CAPN5. In vitro, BEAS-2B cells were transfected with CAPN5 siRNA or CAPN5 plasmid, followed by phosphate-buffered saline (PBS) or cigarette smoke extract (CSE) treatment. The protein expression levels of CAPN5, NF-κB p65, p-p65, IκBα, p-IκBα and apoptosis proteins (BCL-2, BAX) were measured by WB. Flow cytometry (FCM) was performed to analyze the cell apoptosis index.

RESULTS

CAPN5 was mainly expressed in the airway epithelium and significantly decreased in the COPD-smoker and emphysema-mouse groups. Silencing CAPN5 significantly decreased the protein expression of BCL-2, IκBα, and increased p-p65 and BAX protein expression. Additionally, an increased apoptosis index was detected after silencing CAPN5. Moreover, overexpression of CAPN5 partly inhibited IκBα degradation and p65 activation, and reduced CSE-induced inflammation and apoptosis.

CONCLUSIONS

These combined results indicate that CAPN5 could protect against CSE-induced apoptosis and inflammation, which may provide a potential therapeutic target for smoking-related COPD.

Calpain-calpastatin system and cancer progression

The calpain system is required by many important physiological processes, including the cell cycle, cytoskeleton remodelling, cellular proliferation, migration, cancer cell invasion, metastasis, survival, autophagy, apoptosis and signalling, as well as the pathogenesis of a wide range of disorders, in which it may function to promote tumorigenesis. Calpains are intracellular conserved calcium-activated neutral cysteine proteinases that are involved in mediating cancer progression via catalysing and regulating the proteolysis of their specific substrates, which are important signalling molecules during cancer progression. μ-calpain, m-calpain, and their specific inhibitor calpastatin are the three molecules originally identified as comprising the calpain system and they contain several crucial domains, specific motifs, and functional sites. A large amount of data supports the roles of the calpain-calpastatin system in cancer progression via regulation of cellular adhesion, proliferation, invasion, metastasis, and cellular survival and death, as well as inflammation and angiogenesis during tumorigenesis, implying that the inhibition of calpain activity may be a potential anti-cancer intervention strategy targeting cancer cell survival, invasion and chemotherapy resistance.

CAPN5 genetic inactivation phenotype supports therapeutic inhibition trials

Small molecule pharmacological inhibition of dominant human genetic disease is a feasible treatment that does not rely on the development of individual, patient-specific gene therapy vectors. However, the consequences of protein inhibition as a clinical therapeutic are not well-studied. In advance of human therapeutic trials for CAPN5 vitreoretinopathy, genetic inactivation can be used to infer the effect of protein inhibition in vivo. We created a photoreceptor-specific knockout (KO) mouse for Capn5 and compared the retinal phenotype to both wild-type and an existing Capn5 KO mouse model. In humans, CAPN5 loss-of-function (LOF) gene variants were ascertained in large exome databases from 60,706 unrelated subjects without severe disease phenotypes. Ocular examination of the retina of Capn5 KO mice by histology and electroretinography showed no significant abnormalities. In humans, there were 22 LOF CAPN5 variants located throughout the gene and in all major protein domains. Structural modeling of coding variants showed these LOF variants were nearby known disease-causing variants within the proteolytic core and in regions of high homology between human CAPN5 and 150 homologs, yet the LOF of CAPN5 was tolerated as opposed to gain-of-function disease-causing variants. These results indicate that localized inhibition of CAPN5 is a viable strategy for hyperactivating disease alleles.

Molecular dynamic simulations of the catalytic subunit of calpains 1, 2, 5, and 10: Structural analysis with an aim toward drug design

Calpains are cysteine proteases involved in the development of several human chronic illnesses such as neurodegenerative diseases, cardiovascular ailments, diabetes, and obesity which constitutes them into possible therapeutic targets. Here, using molecular dynamic simulations and docking, we studied the binding of known inhibitors to representative members of classical and nonclassical calpains. Our aim is to gain better understanding on the inhibition mechanism of calpains and to develop better and more specific inhibitors. Our atomistic models confirmed the importance of calcium ions for the structure of calpains and, as a consequence, their functionality. With these models and their subsequent use in molecular docking, essential structural requirements were identified for the binding of ligands to the calpain catalytic site that provide useful information for the design of new selective calpain inhibitors.

An anti-CAPN5 intracellular antibody acts as an inhibitor of CAPN5-mediated neuronal degeneration

CAPN5 has been linked to autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV). Activation of CAPN5 may increase proteolysis and degradation of a wide range of substrates to induce degeneration in the retina and the nerve system. Thus, we developed an inhibitory intracellular single chain variable fragment (scFv) against CAPN5 as a potential way to rescue degeneration in ADNIV disease or in neuronal degeneration. We report that overexpression CAPN5 increases the levels of the auto-inflammatory factors toll like receptor 4 (TLR4), interleukin 1 alpha (IL1alpha), tumor necrosis factor alpha (TNFalpha) and activated caspase 3 in 661W photoreceptor-like cells and SHSY5Y neuronal-like cells. Both C4 and C8 scFvs specifically recognize human/mouse CAPN5 in 661W cells and SHSY5Y cells, moreover, both the C4 and C8 scFvs protected cells from CAPN5-induced apoptosis by reducing the levels of activated caspase 3 and caspase 9. The cellular expression C4 scFv reduced levels of the pro-inflammatory factor IL1-alpha activated caspase 3 in cells after CAPN5 overexpression. We suggest that CAPN5 expression has important functional consequences in auto-inflammatory processes, and apoptosis in photoreceptor like cells and neural-like cells. Importantly, the specific intracellular targeting of antibody fragments blocking activation of CAPN5 act as inhibitors of CAPN5 functions in neural like cells, thus, our data provides a novel potential tool for therapy in CAPN5-mediated ADNIV or neurodegenerative diseases.

Calpain 5 is highly expressed in the central nervous system (CNS), carries dual nuclear localization signals, and is associated with nuclear promyelocytic leukemia protein bodies

Calpain 5 (CAPN5) is a non-classical member of the calpain family. It lacks the EF hand motif characteristic of classical calpains but retains catalytic and Ca(2+) binding domains, and it contains a unique C-terminal domain. TRA-3, an ortholog of CAPN5, has been shown to be involved in necrotic cell death in Caenorhabditis elegans. CAPN5 is expressed throughout the CNS, but its expression relative to other calpains and subcellular distribution has not been investigated previously. Based on relative mRNA levels, Capn5 is the second most highly expressed calpain in the rat CNS, with Capn2 mRNA being the most abundant. Unlike classical calpains, CAPN5 is a non-cytosolic protein localized to the nucleus and extra-nuclear locations. CAPN5 possesses two nuclear localization signals (NLS): an N-terminal monopartite NLS and a unique bipartite NLS closer to the C terminus. The C-terminal NLS contains a SUMO-interacting motif that contributes to nuclear localization, and mutation or deletion of both NLS renders CAPN5 exclusively cytosolic. Dual NLS motifs are common among transcription factors. Interestingly, CAPN5 is found in punctate domains associated with promyelocytic leukemia (PML) protein within the nucleus. PML nuclear bodies are implicated in transcriptional regulation, cell differentiation, cellular response to stress, viral defense, apoptosis, and cell senescence as well as protein sequestration, modification, and degradation. The roles of nuclear CAPN5 remain to be determined.

The calpain system and cancer

The calpains are a conserved family of cysteine proteinases that catalyse the controlled proteolysis of many specific substrates. Calpain activity is implicated in several fundamental physiological processes, including cytoskeletal remodelling, cellular signalling, apoptosis and cell survival. Calpain expression is altered during tumorigenesis, and the proteolysis of numerous substrates, such as inhibitors of nuclear factor-κB (IκB), focal adhesion proteins (including, focal adhesion kinase and talin) and proto-oncogenes (for example, MYC), has been implicated in tumour pathogenesis. Recent evidence indicates that the increased expression of certain family members might influence the response to cancer therapies, providing justification for the development of novel calpain inhibitors.

Calpain chronicle--an enzyme family under multidisciplinary characterization

Calpain is an intracellular Ca2+-dependent cysteine protease (EC 3.4.22.17; Clan CA, family C02) discovered in 1964. It was also called CANP (Ca2+-activated neutral protease) as well as CASF, CDP, KAF, etc. until 1990. Calpains are found in almost all eukaryotes and a few bacteria, but not in archaebacteria. Calpains have a limited proteolytic activity, and function to transform or modulate their substrates' structures and activities; they are therefore called, "modulator proteases." In the human genome, 15 genes--CAPN1, CAPN2, etc.--encode a calpain-like protease domain. Their products are calpain homologs with divergent structures and various combinations of functional domains, including Ca2+-binding and microtubule-interaction domains. Genetic studies have linked calpain deficiencies to a variety of defects in many different organisms, including lethality, muscular dystrophies, gastropathy, and diabetes. This review of the study of calpains focuses especially on recent findings about their structure-function relationships. These discoveries have been greatly aided by the development of 3D structural studies and genetic models.

Family-based analysis of candidate genes for polycystic ovary syndrome

CONTEXT

Polycystic ovary syndrome (PCOS) is a complex disorder having both genetic and environmental components. A number of association studies based on candidate genes have reported significant association, but few have been replicated. D19S884, a polymorphic marker in fibrillin 3 (FBN3), is one of the few association findings that has been replicated in independent sets of families.

OBJECTIVE

The aims of the study are: 1) to genotype single nucleotide polymorphisms (SNPs) in the region of D19S884; and 2) to follow up with an independent data set, published results reporting evidence for PCOS candidate gene associations.

DESIGN

The transmission disequilibrium test (TDT) was used to analyze linkage and association between PCOS and SNPs in candidate genes previously reported by us and by others as significantly associated with PCOS.

SETTING

The study was conducted at academic medical centers.

PATIENTS OR OTHER PARTICIPANTS

A total of 453 families having a proband with PCOS participated in the study. Sisters with PCOS were also included. There was a total of 502 probands and sisters with PCOS.

INTERVENTION(S)

There were no interventions.

MAIN OUTCOME MEASURE(S)

The outcome measure was transmission frequency of SNP alleles.

RESULTS

We identified a six-SNP haplotype block spanning a 6.7-kb region on chromosome 19p13.2 that includes D19S884. SNP haplotype allele-C alone and in combination with D19S884-allele 8 is significantly associated with PCOS: haplotype-C TDT chi(2) = 10.0 (P = 0.0016) and haplotype-C/A8 TDT chi(2) = 7.6 (P = 0.006). SNPs in four of the other 26 putative candidate genes that were tested using the TDT were nominally significant (ACVR2A, POMC, FEM1B, and SGTA). One SNP in POMC (rs12473543, chi(2) = 9.1; P(corrected) = 0.042) is significant after correction for multiple testing.

CONCLUSIONS

A polymorphic variant, D19S884, in FBN3 is associated with risk of PCOS. POMC is also a candidate gene of interest.

Is pharmacogenomics our future? Metformin, ovulation and polymorphism of the STK11 gene in polycystic ovary syndrome

Evaluation of: Legro RS, Barnhart HX, Schlaff WD et al.: Ovulatory response to treatment of polycystic ovary syndrome is associated with a polymorphism in the STK11 gene. J. Clin. Endocrinol. Metab. 93(3), 792-800 (2008). The current study by Legro et al. is a substudy of the recent multicenter, double-blinded, prospective study Pregnancy in Polycystic Ovary Syndrome. Legro et al. randomly assigned 626 infertile women with polycystic ovary syndrome to receive 50 mg clomiphene citrate plus placebo (n = 209), 2 g extended-release metformin plus placebo (n = 208), or a combination of metformin and clomiphene (n = 209) for up to six cycles. Of 626 patients in the original study, 312 women participated in the pharmacogenetic substudy; 98 received metformin XR (2 g/day), 102 clomiphene and 112 combined clomiphene-metformin XR treatment. This study was designed "to identify predictive genetic polymorphism and other determinants of ovulatory response" in prospective fashion. Candidate genes tested included estrogen receptor 1 (ESR1), CYP genes (CYP2C9 and CYP2D6) and STK11. STK11, formerly known as LKB1, is a serine-threonine kinase gene expressed in the liver, which phosphorylates and activates AMP-activated protein kinase. It was shown to be a site of metformin action. The C allele of a SNP in the STK11 gene was associated with a significantly decreased chance of ovulation in polycystic ovary syndrome women treated with metformin. In analysis of ovulation per cycle, the adjusted odds ratio for CC versus GG (wild-type normal) was 0.30 (95% CI: 0.14-0.66) and the odds ratio for CG versus GG was 0.30 (95% CI: 0.14-0.66). This elegant study is of great importance because despite treatment, many women with polycystic ovary syndrome fail to ovulate, 24.9% in the clomiphene group, 44.7% in the metformin group and 16.7% in the clomiphene-metformin group.

Calpain5 expression is decreased in endometriosis and regulated by HOXA10 in human endometrial cells

Calpains have been implicated in the regulation of apoptosis. Here, we identified Calpain5 as a target of HOXA10 transcriptional regulation in endometrial cells as well as its aberrant regulation in endometriosis. Histologically confirmed biopsies of endometriosis were obtained from 20 women. Eutopic endometrium was collected by endometrial biopsy from 30 controls and from the 20 subjects with endometriosis. First trimester decidual samples were obtained from five subjects at the time of pregnancy termination. Immunohistochemistry was used to identify Calpain5 expression. Calpain5 was expressed in endometrial stromal and glandular cells throughout the menstrual cycle and in decidua. Calpain5 protein expression was decreased in both stromal and glandular cells from women with endometriosis compared with that of fertile controls. Human endometrial stromal and epithelial cell lines were transfected with pcDNA/HOXA10, HOXA10 siRNA or respective controls. Quantitative real-time RT-PCR was performed to determine expression of HOXA10 and Calpain5 in each group. Transfection of HESC cells with an HOXA10 expression construct led to increased Calpain5 expression, whereas transfection with siRNA resulted in decreased expression. In conclusion, Calpain5 expression is regulated by HOXA10. Calpain5 expression was decreased in endometriosis likely as a result of decreased HOXA10 expression. Decreased apoptosis in endometrial cells may promote the development of endometriosis through a pathway involving HOXA10, Calpain5 and caspase.

FEM1A and FEM1B: novel candidate genes for polycystic ovary syndrome

BACKGROUND

Human homologs (FEM1A, FEM1B, FEM1C) of nematode sex determination genes are candidate genes for polycystic ovary syndrome (PCOS). We previously identified a FEM1A mutation (H500Y) in a woman with PCOS; FEM1B has been implicated in insulin secretion.

METHODS

Women with and without PCOS (287 cases, 187 controls) were genotyped for H500Y and six FEM1A single nucleotide polymorphisms (SNPs), five FEM1B SNPs and five FEM1C SNPs. SNPs and haplotypes were determined and tested for association with PCOS and component phenotypes.

RESULTS

No subject carried the FEM1A H500Y mutation. FEM1A SNPs rs8111933 (P = 0.001) and rs12460989 (P = 0.046) were associated with an increased likelihood of PCOS whereas FEM1A SNP rs1044386 was associated with a reduced probability of PCOS (P = 0.013). FEM1B SNP rs10152450 and a linked SNP were associated with a reduced likelihood of PCOS (P = 0.005), and lower homeostasis model assessment (HOMA) for beta-cell function (HOMA-%B, P = 0.011) and lower HOMA for insulin resistance (HOMA-IR, P = 0.018). FEM1B SNP rs12909277 was associated with lower HOMA-%B (P = 0.008) and lower HOMA-IR (P = 0.037). Haplotype associations were consistent with SNP results, and also revealed association of FEM1B haplotype TGAGG with increased HOMA-%B (P = 0.007) and HOMA-IR (P = 0.024). FEM1C variants were not associated with PCOS.

CONCLUSIONS

This study presents evidence suggesting a role for FEM1A and FEM1B in the pathogenesis of PCOS. Only FEM1B variants were associated with insulin-related traits in PCOS women, consistent with prior evidence linking this gene to insulin secretion. Replication of these associations and mechanistic studies will be necessary to establish the role of these genes in PCOS.

Interaction between Calpain 5, Peroxisome proliferator-activated receptor-gamma and Peroxisome proliferator-activated receptor-delta genes: a polygenic approach to obesity

Context

Obesity is a multifactorial disorder, that is, a disease determined by the combined effect of genes and environment. In this context, polygenic approaches are needed.

Objective

To investigate the possibility of the existence of a crosstalk between the CALPAIN 10 homologue CALPAIN 5 and nuclear receptors of the peroxisome proliferator-activated receptors family.

Design

Cross-sectional, genetic association study and gene-gene interaction analysis.

Subjects

The study sample comprise 1953 individuals, 725 obese (defined as body mass index ≥ 30) and 1228 non obese subjects.

Results

In the monogenic analysis, only the peroxisome proliferator-activated receptor delta (PPARD) gene was associated with obesity (OR = 1.43 [1.04–1.97], p = 0.027). In addition, we have found a significant interaction between CAPN5 and PPARD genes (p = 0.038) that reduces the risk for obesity in a 55%.

Conclusion

Our results suggest that CAPN5 and PPARD gene products may also interact in vivo.

Association study between single nucleotide polymorphisms in the VEGF gene and polycystic ovary syndrome

OBJECTIVE

To investigate single nucleotide polymorphisms (SNPs) in vascular endothelial growth factor (VEGF) gene that have significant associations with the pathogenesis of polycystic ovary syndrome (PCOS) in a Korean population.

DESIGN

Case-control study.

SETTING

University-based hospital.

PATIENT(S)

One hundred thirty-four patients with PCOS and 100 healthy women as controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Frequencies of genotypes for SNPs in VEGF gene, which were specifically expressed in a Korean population.

RESULT(S)

After genotypic analysis, we found that among 10 SNPs, one novel SNP at site +9812 and one known SNP at site +13553 have P values lower than .05 (+9812: odds ratio [95% confidence interval] 0.61 [0.39-0.95]; +13553: odds ratio [95% confidence interval] 0.59 [0.37-0.93]) and one haplotype (ht4) also has a P value in the significant range (odds ratio [95% confidence interval] 0.34 [0.16-0.74]).

CONCLUSION(S)

We concluded that one novel SNP at +9812 site, one known SNP at +13553 site, and one selected haplotype in the VEGF gene have a high possibility of significant associations with the pathogenesis of PCOS in a Korean population.

Calpain-5 gene variants are associated with diastolic blood pressure and cholesterol levels

Background

Genes implicated in common complex disorders such as obesity, type 2 diabetes mellitus (T2DM) or cardiovascular diseases are not disease specific, since clinically related disorders also share genetic components. Cysteine protease Calpain 10 (CAPN10) has been associated with T2DM, hypertension, hypercholesterolemia, increased body mass index (BMI) and polycystic ovary syndrome (PCOS), a reproductive disorder of women in which isunlin resistance seems to play a pathogenic role. The calpain 5 gene (CAPN5) encodes a protein homologue of CAPN10. CAPN5 has been previously associated with PCOS by our group. In this new study, we have analysed the association of four CAPN5 gene variants(rs948976A>G, rs4945140G>A, rs2233546C>T and rs2233549G>A) with several cardiovascular risk factors related to metabolic syndrome in general population.

Methods

Anthropometric measurements, blood pressure, insulin, glucose and lipid profiles were determined in 606 individuals randomly chosen from a cross-sectional population-based epidemiological survey in the province of Segovia in Central Spain (Castille), recruited to investigate the prevalence of anthropometric and physiological parameters related to obesity and other components of the metabolic syndrome. Genotypes at the four polymorphic loci in CAPN5 gene were detected by polymerase chain reaction (PCR).

Results

Genotype association analysis was significant for BMI (p ≤ 0.041), diastolic blood pressure (p = 0.015) and HDL-cholesterol levels (p = 0.025). Different CAPN5 haplotypes were also associated with diastolic blood pressure (DBP) (0.0005 ≤ p ≤ 0.006) and total cholesterol levels (0.001 ≤ p ≤ 0.029). In addition, the AACA haplotype, over-represented in obese individuals, is also more frequent in individuals with metabolic syndrome defined by ATPIII criteria (p = 0.029).

Conclusion

As its homologue CAPN10, CAPN5 seems to influence traits related to increased risk for cardiovascular diseases. Our results also may suggest CAPN5 as a candidate gene for metabolic syndrome.

The therapeutic potential of the calpain family: new aspects

The calpain family is a group of cysteine proteases unique in their dependency on calcium to attain functionally active forms. Calpains are involved in a wide range of cellular calcium-regulated functions, including signal transduction, cell proliferation and differentiation, and apoptosis. Moreover, altered calpain activity has been observed in several human diseases. Specific calpain inhibitors hold promise for the treatment of neuromuscular and neurodegenerative diseases in which calpains have been shown to be upregulated (e.g. Parkinson's disease and Duchenne muscular dystrophy). Conversely, calpain activators could be a useful approach for those diseases where reduced calpain activity has been observed, such as type 2 diabetes or metabolic syndrome.