The cysteine-rich protein family of highly related LIM domain proteins

TGF-β signaling promotes desmoid tumor formation via CSRP2 upregulation

Desmoid tumors (DTs), also called desmoid-type fibromatoses, are locally aggressive tumors of mesenchymal origin. In the present study, we developed a novel mouse model of DTs by inducing a local mutation in the Ctnnb1 gene, encoding β-catenin in PDGFRA-positive stromal cells, by subcutaneous injection of 4-hydroxy-tamoxifen. Tumors in this model resembled histologically clinical samples from DT patients and showed strong phosphorylation of nuclear SMAD2. Knockout of SMAD4 in the model significantly suppressed tumor growth. Proteomic analysis revealed that SMAD4 knockout reduced the level of Cysteine-and-Glycine-Rich Protein 2 (CSRP2) in DTs, and treatment of DT-derived cells with a TGF-β receptor inhibitor reduced CSRP2 RNA levels. Knockdown of CSRP2 in DT cells significantly suppressed their proliferation. These results indicate that the TGF-β/CSRP2 axis is a potential therapeutic target for DTs downstream of TGF-β signaling.

MYH1F promotes the proliferation and differentiation of chicken skeletal muscle satellite cells into myotubes

In diploid organisms, interactions between alleles determine phenotypic variation. In previous experiments, only MYH1F was found to show both ASE (spatiotemporal allele-specific expression) and TRD (allelic transmission ratio distortion) characteristics in the pectoral muscle by comparing the genome-wide allele lists of hybrid populations (F1) of meat- and egg- type chickens. In addition, MYH1F is a member of the MYH gene family, which plays an important role in skeletal muscle and non-muscle cells of animals, but the specific expression and function of this gene in chickens are still unknown. Therefore, qRT-PCR was used to detect the expression of MYH1F in different tissues of chicken. Proliferation and differentiation of chicken skeletal muscle satellite cells (SMSCs) have been detected by transfection of MYH1F-specific small interfering RNA (siRNA). The results showed that the expression of MYH1F in chicken skeletal muscle was higher than that in other tissues. Combined with CCK-8 assay, EdU assay, immunofluorescence, and Western blot Assay, it was found that MYH1F knockdown could significantly suppress the proliferation of chicken SMSCs and depress the differentiation and fusion of the cells. These results suggest that MYH1F plays a critical role in myogenesis in poultry, which is of great significance for exploring the regulatory mechanisms of muscle development and improving animal productivity.

Actin cytoskeleton depolymerization increases matrix metalloproteinase gene expression in breast cancer cells by promoting translocation of cysteine-rich protein 2 to the nucleus

The actin cytoskeleton plays a critical role in cancer cell invasion and metastasis; however, the coordination of its multiple functions remains unclear. Actin dynamics in the cytoplasm control the formation of invadopodia, which are membrane protrusions that facilitate cancer cell invasion by focusing the secretion of extracellular matrix-degrading enzymes, including matrix metalloproteinases (MMPs). In this study, we investigated the nuclear role of cysteine-rich protein 2 (CRP2), a two LIM domain-containing F-actin-binding protein that we previously identified as a cytoskeletal component of invadopodia, in breast cancer cells. We found that F-actin depolymerization stimulates the translocation of CRP2 into the nucleus, resulting in an increase in the transcript levels of pro-invasive and pro-metastatic genes, including several members of the MMP gene family. We demonstrate that in the nucleus, CRP2 interacts with the transcription factor serum response factor (SRF), which is crucial for the expression of MMP-9 and MMP-13. Our data suggest that CRP2 and SRF cooperate to modulate of MMP expression levels. Furthermore, Kaplan-Meier analysis revealed a significant association between high-level expression of SRF and shorter overall survival and distant metastasis-free survival in breast cancer patients with a high CRP2 expression profile. Our findings suggest a model in which CRP2 mediates the coordination of cytoplasmic and nuclear processes driven by actin dynamics, ultimately resulting in the induction of invasive and metastatic behavior in breast cancer cells.

Computational analysis of the flexibility in the disordered linker region connecting LIM domains in cysteine–glycine-rich protein

One of the key proteins that are present in the Z-disc of cardiac tissues, CSRP3, has been implicated in dilated and hypertrophic cardiomyopathy leading to heart failure. Although multiple cardiomyopathy-related mutations have been reported to reside on the two LIM domains and the disordered regions connecting the domains in this protein, the exact role of the disordered linker region is not clear. The linker harbors a few post-translational modification sites and is expected to be a regulatory site. We have carried out evolutionary studies on 5614 homologs spanning across taxa. We also performed molecular dynamics simulations of full-length CSRP3 to show that the length variations and conformational flexibility of the disordered linker could provide additional levels of functional modulation. Finally, we show that the CSRP3 homologs with widely different lengths of the linker regions could display diversity in their functional specifications. The present study provides a useful perspective to our understanding of the evolution of the disordered region between CSRP3 LIM domains.

Role of CRP2-MRTF interaction in functions of myofibroblasts

Inflammatory response induces phenotypic modulation of fibroblasts into myofibroblasts. Although transforming growth factor-βs (TGF-βs) evoke such transition, the details of the mechanism are still unknown. Here, we report that a LIM domain protein, cysteine-and glycine-rich protein 2 (CSRP2 [CRP2]) plays a vital role in the functional expression profile in myofibroblasts and cancer-associated fibroblasts (CAFs). Knock-down of CRP2 severely inhibits the expression of smooth muscle cell (SMC) genes, cell motility, and CAF-mediated collective invasion of epidermoid carcinoma. We elucidate the following molecular bases: CRP2 directly binds to myocardin-related transcription factors (MRTF-A/B [MRTFs]) and serum response factor (SRF) and stabilizes the MRTF/SRF/CArG-box complex to activate SMC gene expression. Furthermore, a three-dimensional structural analysis of CRP2 identifies the amino acids required for the CRP2-MRTF-A interaction. Polar amino acids in the C-terminal half (serine-152, glutamate-154, serine-155, threonine-156, threonine-157, and threonine-159 in human CRP2) are responsible for direct binding to MRTF-A. On the other hand, hydrophobic amino acids outside the consensus sequence of the LIM domain (tryptophan-139, phenylalanine-144, leucine-153, and leucine-158 in human CRP2) play a role in stabilizing the unique structure of the LIM domain.Key words: CRP2, 3D structure, myocardin-related transcription factor, myofibroblast, cancer-associated fibroblasts.

Cysteine-Rich LIM-Only Protein 4 (CRP4) Promotes Atherogenesis in the ApoE-/- Mouse Model

Vascular smooth muscle cells (VSMCs) can switch from their contractile state to a synthetic phenotype resulting in high migratory and proliferative capacity and driving atherosclerotic lesion formation. The cysteine-rich LIM-only protein 4 (CRP4) reportedly modulates VSM-like transcriptional signatures, which are perturbed in VSMCs undergoing phenotypic switching. Thus, we hypothesized that CRP4 contributes to adverse VSMC behaviours and thereby to atherogenesis in vivo. The atherogenic properties of CRP4 were investigated in plaque-prone apolipoprotein E (ApoE) and CRP4 double-knockout (dKO) as well as ApoE-deficient CRP4 wildtype mice. dKO mice exhibited lower plaque numbers and lesion areas as well as a reduced content of α-smooth muscle actin positive cells in the lesion area, while lesion-associated cell proliferation was elevated in vessels lacking CRP4. Reduced plaque volumes in dKO correlated with significantly less intra-plaque oxidized low-density lipoprotein (oxLDL), presumably due to upregulation of the antioxidant factor peroxiredoxin-4 (PRDX4). This study identifies CRP4 as a novel pro-atherogenic factor that facilitates plaque oxLDL deposition and identifies the invasion of atherosclerotic lesions by VSMCs as important determinants of plaque vulnerability. Thus, targeting of VSMC CRP4 should be considered in plaque-stabilizing pharmacological strategies.

Fibroblast mechanosensing, SKI and Hippo signaling and the cardiac fibroblast phenotype: Looking beyond TGF-β

Cardiac fibroblast activation to hyper-synthetic myofibroblasts following a pathological stimulus or in response to a substrate with increased stiffness may be a key tipping point for the evolution of cardiac fibrosis. Cardiac fibrosis per se is associated with progressive loss of heart pump function and is a primary contributor to heart failure. While TGF-β is a common cytokine stimulus associated with fibroblast activation, a druggable target to quell this driver of fibrosis has remained an elusive therapeutic goal due to its ubiquitous use by different cell types and also in the signaling complexity associated with SMADs and other effector pathways. More recently, mechanical stimulus of fibroblastic cells has been revealed as a major point of activation; this includes cardiac fibroblasts. Further, the complexity of TGF-β signaling has been offset by the discovery of members of the SKI family of proteins and their inherent anti-fibrotic properties. In this respect, SKI is a protein that may bind a number of TGF-β associated proteins including SMADs, as well as signaling proteins from other pathways, including Hippo. As SKI is also known to directly deactivate cardiac myofibroblasts to fibroblasts, this mode of action is a putative candidate for further study into the amelioration of cardiac fibrosis. Herein we provide a synthesis of this topic and highlight novel candidate pathways to explore in the treatment of cardiac fibrosis.

Characterization of an MLP Homologue from Haemaphysalis longicornis (Acari: Ixodidae) Ticks

Members of the cysteine-rich protein (CRP) family are known to participate in muscle development in vertebrates. Muscle LIM protein (MLP) belongs to the CRP family and has an important function in the differentiation and proliferation of muscle cells. In this study, the full-length cDNA encoding MLP from Haemaphysalis longicornis (H. longicornis; HLMLP) ticks was obtained by 5' rapid amplification of cDNA ends (RACE). To verify the transcriptional status of MLP in ticks, HLMLP gene expression was assessed during various developmental stages by real-time PCR (RT-PCR). Interestingly, HLMLP expression in the integument was significantly (P < 0.01) higher than that observed in other tested tissues of engorged adult ticks. In addition, HLMLP mRNA levels were significantly downregulated in response to thermal stress at 4 °C for 48 h. Furthermore, recombinant HLMLP was expressed in Escherichia coli, and Western blot analysis showed that rabbit antiserum against H. longicornis adults recognized HLMLP and MLPs from different ticks. Ten 3-month-old rabbits that had never been exposed to ticks were used for the immunization and challenge experiments. The rabbits were divided into two groups of five rabbits each, where rabbits in the first group were immunized with HLMLP, while those in the second group were immunized with phosphate-buffered saline (PBS) diluent as controls. The vaccination of rabbits with the recombinant HLMLP conferred partial protective immunity against ticks, resulting in 20.00% mortality and a 17.44% reduction in the engorgement weight of adult ticks. These results suggest that HLMLP is not ideal as a candidate for use in anti-tick vaccines. However, the results of this study generated novel information on the MLP gene in H. longicornis and provide a basis for further investigation of the function of this gene that could potentially lead to a better understanding of the mechanism of myofiber determination and transformation.

MEF2 as upstream regulator of the transcriptome signature in human skeletal muscle during unloading

Our understanding of skeletal muscle structural and functional alterations during unloading has increased in recent decades, yet the molecular mechanisms underpinning these changes have only started to be unraveled. The purpose of the current investigation was to assess changes in skeletal muscle gene expression after 21 days of bed rest, with a particular focus on predicting upstream regulators of muscle disuse. Additionally, the association between differential microRNA expression and the transcriptome signature of bed rest were investigated. mRNAs from musculus vastus lateralis biopsies obtained from 12 men before and after the bed rest were analyzed using a microarray. There were 54 significantly upregulated probesets after bed rest, whereas 103 probesets were downregulated (false discovery rate 10%; fold-change cutoff ≥1.5). Among the upregulated genes, transcripts related to denervation-induced alterations in skeletal muscle were identified, e.g., acetylcholine receptor subunit delta and perinatal myosin. The most downregulated transcripts were functionally enriched for mitochondrial genes and genes involved in mitochondrial biogenesis, followed by a large number of contractile fiber components. Upstream regulator analysis identified a robust inhibition of the myocyte enhancer factor-2 (MEF2) family, in particular MEF2C, which was suggested to act upstream of several key downregulated genes, most notably peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α)/peroxisome proliferator-activated receptors (PPARs) and CRSP3. Only a few microRNAs were identified as playing a role in the overall transcriptome picture induced by sustained bed rest. Our results suggest that the MEF2 family is a key regulator underlying the transcriptional signature of bed rest and, hence, ultimately also skeletal muscle alterations induced by systemic unloading in humans.

Cyclic stretch-induced Crp3 sensitizes vascular smooth muscle cells to apoptosis during vein arterialization remodeling

Vein graft failure limits the long-term patency of the saphenous vein used as a conduit for coronary artery bypass graft. Early graft adaptation involves some degree of intima hyperplasia to sustain the hemodynamic stress, but the progress to occlusion in some veins remains unclear. We have demonstrated that stretch-induced up-regulation of cysteine and glycine-rich protein 3 (Crp3) in rat jugular vein and human saphenous vein in response to arterialization. Here, we developed a Crp3-KO rat to investigate the role of Crp3 in vascular remodeling. After 28 days jugular vein arterialization, the intima layer was 3-fold thicker in the Crp3-KO that showed comparable smooth muscle cells (SMC) proliferation but an absence of early apoptosis observed in the wild-type rat (WT). We then investigated the role of Crp3 in early integrin-mediated signaling apoptosis in isolated jugular SMC. Interestingly, under basal conditions, ceramide treatment failed to induce apoptosis in both WT and Crp3-KO SMC. Under stretch, Crp3 expression increased in WT SMC and ceramide induced apoptosis. Immunoblotting analysis indicated that ceramide stretch-induced apoptosis in SMC is accompanied by a decrease in the phosphorylation status of both Fak and Akt, leading to an increase in Bax expression and caspase-3 cleavage. In contrast, ceramide failed to decrease Fak and Akt phosphorylation in Crp3-KO SMC and, therefore, there was no downstream induction of Bax expression and effector caspase-3 cleavage. Taken together, we provide evidence that stretch-induced Crp3 modulates vein remodeling in response to arterialization by sensitizing SMC to apoptosis.

Molecular cloning, characterization, and expression analysis of the three cysteine and glycine-rich protein genes in the Chinese fire-bellied newt Cynops orientalis

The cysteine- and glycine-rich protein (CRP) family members, including the cysteine- and glycine-rich protein 1 (CSRP1), cysteine- and glycine-rich protein 2 (CSRP2), and the cysteine- and glycine-rich protein 3 (CSRP3), have exhibited various cellular functions during cell development and differentiation. However, the sequences of the three CSRP genes and their functions are still poorly understood in newts. In this study, we cloned the complete open reading frame (ORF) sequences of the three CSRP genes from the Chinese fire-bellied newt, Cynops orientalis (C. orientalis). The complete ORF sequences of Co-CSRP1, Co-CSRP2, and Co-CSRP3 were 582, 582, and 576bp, respectively, and encoded 193, 193, and 191 amino acids, respectively. The deduced amino acid sequences of the three CRP members showed high similarities with that of other species, particularly, with amphibians. Co-CSRP1 was highly expressed in the kidney, limb, and stomach, however, the expression was low in the spleen, heart, intestine, liver, and tail (P<0.05). The mRNA expression of Co-CSRP2 was higher in the kidney and heart than that in other organs (P<0.05). It was observed that Co-CSRP3 was only expressed in the heart, limb, and tail. The mRNA expression of Co-CSRP1 and Co-CSRP3 was lower in the digits in comparison to other limb segments. However, there was no significant difference of Co-CSRP2 mRNA expression in the four limb segments. The Co-CSRP1 and Co-CSRP2 mRNA expressions were significantly increased, whereas the expression of Co-CSRP3 was remarkably decreased during the limb regeneration. This study will provide useful information for further elucidating the role of Co-CSRP genes during newt limb regeneration.

When signalling goes wrong: pathogenic variants in structural and signalling proteins causing cardiomyopathies

Cardiomyopathies are a diverse group of cardiac disorders with distinct phenotypes, depending on the proteins and pathways affected. A substantial proportion of cardiomyopathies are inherited and those will be the focus of this review article. With the wide application of high-throughput sequencing in the practice of clinical genetics, the roles of novel genes in cardiomyopathies are recognised. Here, we focus on a subgroup of cardiomyopathy genes [TTN, FHL1, CSRP3, FLNC and PLN, coding for Titin, Four and a Half LIM domain 1, Muscle LIM Protein, Filamin C and Phospholamban, respectively], which, despite their diverse biological functions, all have important signalling functions in the heart, suggesting that disturbances in signalling networks can contribute to cardiomyopathies.

Overview of the Muscle Cytoskeleton

Cardiac and skeletal striated muscles are intricately designed machines responsible for muscle contraction. Coordination of the basic contractile unit, the sarcomere, and the complex cytoskeletal networks are critical for contractile activity. The sarcomere is comprised of precisely organized individual filament systems that include thin (actin), thick (myosin), titin, and nebulin. Connecting the sarcomere to other organelles (e.g., mitochondria and nucleus) and serving as the scaffold to maintain cellular integrity are the intermediate filaments. The costamere, on the other hand, tethers the sarcomere to the cell membrane. Unique structures like the intercalated disc in cardiac muscle and the myotendinous junction in skeletal muscle help synchronize and transmit force. Intense investigation has been done on many of the proteins that make up these cytoskeletal assemblies. Yet the details of their function and how they interconnect have just started to be elucidated. A vast number of human myopathies are contributed to mutations in muscle proteins; thus understanding their basic function provides a mechanistic understanding of muscle disorders. In this review, we highlight the components of striated muscle with respect to their interactions, signaling pathways, functions, and connections to disease. © 2017 American Physiological Society. Compr Physiol 7:891-944, 2017.

Nociceptive DRG neurons express muscle lim protein upon axonal injury

Muscle lim protein (MLP) has long been regarded as a cytosolic and nuclear muscular protein. Here, we show that MLP is also expressed in a subpopulation of adult rat dorsal root ganglia (DRG) neurons in response to axonal injury, while the protein was not detectable in naïve cells. Detailed immunohistochemical analysis of L4/L5 DRG revealed ~3% of MLP-positive neurons 2 days after complete sciatic nerve crush and maximum ~10% after 4–14 days. Similarly, in mixed cultures from cervical, thoracic, lumbar and sacral DRG ~6% of neurons were MLP-positive after 2 days and maximal 17% after 3 days. In both, histological sections and cell cultures, the protein was detected in the cytosol and axons of small diameter cells, while the nucleus remained devoid. Moreover, the vast majority could not be assigned to any of the well characterized canonical DRG subpopulations at 7 days after nerve injury. However, further analysis in cell culture revealed that the largest population of MLP expressing cells originated from non-peptidergic IB4-positive nociceptive neurons, which lose their ability to bind the lectin upon axotomy. Thus, MLP is mostly expressed in a subset of axotomized nociceptive neurons and can be used as a novel marker for this population of cells.

Muscle LIM Protein: Master regulator of cardiac and skeletal muscle functions

Muscle LIM Protein (MLP) has emerged as a key regulator of striated muscle physiology and pathophysiology. Mutations in cysteine and glycine-rich protein 3 (CSRP3), the gene encoding MLP, are causative of human cardiomyopathies, whereas altered expression patterns are observed in human failing heart and skeletal myopathies. In vitro and in vivo evidences reveal a complex and diverse functional role of MLP in striated muscle, which is determined by its multiple interacting partners and subcellular distribution. Experimental evidence suggests that MLP is implicated in both myogenic differentiation and myocyte cytoarchitecture, although the full spectrum of its intracellular roles still unfolds.

Expression, SNV identification, linkage disequilibrium, and combined genotype association analysis of the muscle-specific gene CSRP3 in Chinese cattle

The cysteine and glycine-rich protein 3 (CSRP3) plays an important role in the myofiber differentiation. Here, we identified five SNVs in all exon and intron regions of the CSRP3 gene using DNA sequencing, PCR-RFLP and forced-PCR-RFLP methods in 554 cattle. Four of the five SNVs were significantly associated with growth performance and carcass traits of the cattle. In addition, we evaluated haplotype frequency and linkage disequilibrium coefficient of five sequence variants. The result of haplotype analysis demonstrated 28 haplotypes present in Qinchuan and two haplotypes in Chinese Holstein. Only haplotypes 1 and 8 were being shared by two populations, haplotype 14 had the highest haplotype frequency in Qinchuan (17.4%) and haplotype 8 had the highest haplotype frequency in Chinese Holstein (94.4%). Statistical analyses of combined genotypes indicated that some combined genotypes were significantly or highly significantly associated with growth and carcass traits in the Qinchuan cattle population. qPCR analyses also showed that bovine CSRP3 gene was exclusively expressed in longissimus dorsi muscle and heart tissues. The data support the high potential of the CSRP3 as a marker gene for the improvement of growth performance and carcass traits in selection programs.

SNV and haplotype analysis reveals new CSRP1 variants associated with growth and carcass traits

The cysteine and glycine-rich protein 1 and 2 genes (CSRP1 and CSRP2) are an effective growth factor in promoting skeletal muscle growth in vitro and vivo. However, in cattle, the information on the CSRP1 and CSRP2 genes is very limited. The aim of this study was to examine the association of the CSRP1 and CSRP2 variants with growth and carcass traits in cattle breeds. Three single nucleotide variants (SNVs) were identified within the bovine CSRP1 gene, whereas CSRP2 gene has not detected any SNVs, using DNA pooled sequencing, PCR-RFLP, and forced PCR-RFLP methods. These SNVs include g. 801T>C (Intron 2), g. 46T>C (Exon 3) and g. 99C>G (Intron 3). Besides, we also investigated haplotype frequencies and linkage disequilibrium (LD) coefficients for three SNVs in all study populations. LD and haplotype structure of CSRP1 were different between breeds. The result of haplotype analysis demonstrated eight haplotype present in QC (Qinchuan) and one haplotype in CH (Chinese Holstein). Only haplotype 1 (TTC), shared by all two populations, comprised 10.74% and 100.00%, of all haplotypes observed in QC and CH, respectively. Haplotype 5 (CTC) had the highest haplotype frequencies in QC (30.98%) and haplotype 1 had the highest haplotype frequencies in CH (100.00%). The statistical analyses indicated that one single SNV and 19 combined haplotypes were significantly or highly significantly associated with growth and carcass traits in the QC cattle population (P<0.05 or P<0.01). Quantitative real-time PCR (qRT-PCR) analyses showed that the bovine CSRP1 and CSRP2 genes were widely expressed in many tissues. The results of this study suggest that the CSRP1 gene possibly is a strong candidate gene that affects growth and carcass traits in the Chinese beef cattle breeding.

Four-and-a-half LIM domains protein 2 (FHL2) is associated with the development of craniofacial musculature in the teleost fish Sparus aurata

Four-and-a-half LIM domains protein 2 (FHL2) is involved in major cellular mechanisms such as regulation of gene transcription and cytoskeleton modulation, participating in physiological control of cardiogenesis and osteogenesis. Knowledge on underlying mechanisms is, however, limited. We present here new data on FHL2 protein and its role during vertebrate development using a marine teleost fish, the gilthead seabream (Sparus aurata L.). In silico comparison of vertebrate protein sequences and prediction of LIM domain three-dimensional structure revealed a high degree of conservation, suggesting a conserved function throughout evolution. Determination of sites and levels of FHL2 gene expression in seabream indicated a central role for FHL2 in the development of heart and craniofacial musculature, and a potential role in tissue calcification. Our data confirmed the key role of FHL2 protein during vertebrate development and gave new insights into its particular involvement in craniofacial muscle development and specificity for slow fibers.

Early depression of Ankrd2 and Csrp3 mRNAs in the polyribosomal and whole tissue fractions in skeletal muscle with decreased voluntary running

The wheel-lock (WL) model for depressed ambulatory activity in rats has shown metabolic maladies ensuing within 53-173 h after WL begins. We sought to determine if WL beginning after 21-23 days of voluntary running in growing female Wistar rats affected the mRNA profile in the polyribosomal fraction from plantaris muscle shortly following WL. In experiment 1, WL occurred at 0200 and muscles were harvested at 0700 daily at 5 h (WL5h, n = 4), 29 h (WL29h, n = 4), or 53 h (WL53h, n = 4) after WL. Affymetrix Rat Gene 1.0 ST Arrays were used to test the initial question as to whether WL affects mRNA occupancy on skeletal muscle polyribosomes. Using a false discovery rate of 15%, no changes in mRNAs in the polyribosomal fraction were observed at WL29h and eight mRNAs (of over 8,200 identified targets) were altered at WL53h compared with WL5h. Interestingly, two of the six downregulated genes included ankyrin repeat domain 2 (Ankrd2) and cysteine-rich protein 3/muscle LIM protein (Csrp3), both of which encode mechanical stretch sensors and RT-PCR verified their WL-induced decline. In experiment 2, whole muscle mRNA and protein levels were analyzed for Ankrd2 and Csrp3 from the muscles of WL5h (4 original samples + 2 new), WL29h (4 original), WL53h (4 original + 2 new), as well as WL173 h (n = 6 new) and animals that never ran (SED, 4-5 new). Relative to WL5h controls, whole tissue Ankrd2 and Csrp3 mRNAs were lower (P < 0.05) at WL53h, WL173h, and SED; Ankrd2 protein tended to decrease at WL53h (P = 0.054) and Csrp3 protein was less in WL173h and SED rats (P < 0.05). In summary, unique early declines in Ankrd2 and Csrp3 mRNAs were identified with removal of voluntary running, which was subsequently followed by declines in Csrp3 protein levels during longer periods of wheel lock.

LIM domains regulate protein kinase C activity: a novel molecular function

Enigma homolog protein 1 (ENH1) acts as a scaffold that selectively associates protein kinases and transcription factors with cytoskeletal elements. ENH1 comprises an N-terminal PDZ domain and three C-terminal LIM domains. Through the LIM domains ENH1 interacts with the N-terminal region of protein kinase C βI (PKCβI). Here, we show that when ENH1 is co-expressed, PKCβI is translocated from the cytoplasm to the plasma membrane in the absence of any other stimulation. Moreover expression of ENH1 markedly increases PKCβI activity in the absence of PKC activators. A similar activation of PKCβI was observed with co-expression of Cypher1 or Enigma, but not other LIM proteins. The region including the three LIM domains of ENH1 (residues 415-591) appears to be sufficient for this PKCβI activation. Finally, interaction with ENH1 also increases the activity of PKCα and PKCγ, whereas it reduces PKCζ activity. These findings provide strong evidence that ENH1 activates conventional PKCs by directly binding through its LIM domains. Thus, LIM domains have a novel molecular function: the regulation of PKC activities in a PKC isoform-specific manner.

Intronic CArG box regulates cysteine-rich protein 2 expression in the adult but not in developing vasculature

OBJECTIVE

An absence of cysteine-rich protein 2 (CRP2) enhances vascular smooth muscle cell (VSMC) migration and increases neointima formation after arterial injury; therefore, CRP2 plays an important role in the response to vascular injury. The goal of the present study was to elucidate the molecular mechanisms that preserve CRP2 expression in the adult vasculature and thus might serve to inhibit the response to injury.

METHODS AND RESULTS

We generated a series of transgenic mice harboring potential Csrp2 regulatory regions with a lacZ reporter. We determined that the 12-kb first intron was necessary for transgene activity in adult but not in developing vasculature. Within the intron we identified a 6.3-kb region that contains 2 CArG boxes. Serum response factor preferentially bound to CArG2 box in gel mobility shift and chromatin immunoprecipitation assays; additionally, serum response factor coactivator myocardin factors activated CRP2 expression via the CArG2 box. Mutational analysis revealed that CArG2 box was important in directing lacZ expression in VSMC of adult vessels.

CONCLUSIONS

Although CRP2 expression during development is independent of CArG box regulatory sites, CRP2 expression in adult VSMC requires CArG2 element within the first intron. Our results suggest that distinct mechanisms regulate CRP2 expression in VSMC that are controlled by separate embryonic and adult regulatory modules.

Polyclonal antibodies to LIM proteins CRP2 and CRIP2 reveal their subcellular localizations in olfactory precursor cells

In this study, we describe the presence of CRP2 (cysteine- and glycine-rich protein 2) and CRIP2 (cysteine-rich intestinal protein 2), which are members of group 2 LIM proteins, in rat olfactory precursor cells by reverse transcription polymerase chain reaction. We have developed polyclonal antibodies against CRP2 and CRIP2 individually. Specificity of the antibodies was demonstrated by Western blot analysis, using CRP2 and CRIP2 transfected cells. No cross-reactivity was observed between the antibodies. Furthermore, we used the antibodies to determine the expression and localization of CRP2 and CRIP2 in olfactory precursor cells by Western blot analysis and immunofluorescence staining. Our results demonstrated that in undifferentiated olfactory precursor cells CRP2 was distributed both in the nucleus and the cytoplasm, whereas CRIP2 was predominantly localized in the cytoplasm. While the olfactory precursor cells differentiated into end cells, only the expression of CRIP2 would be detected. The function of these LIM proteins in olfactory precursor cells warrants further study.

Induction of CRP3/MLP expression during vein arterialization is dependent on stretch rather than shear stress

AIMS

Cysteine- and glycine-rich protein 3/muscle LIM-domain protein (CRP3/MLP) mediates protein-protein interaction with actin filaments in the heart and is involved in muscle differentiation and vascular remodelling. Here, we assessed the induction of CRP3/MLP expression during arterialization in human and rat veins.

METHODS AND RESULTS

Vascular CRP3/MLP expression was mainly observed in arterial samples from both human and rat. Using quantitative real time RT-PCR, we demonstrated that the CRP3/MLP expression was 10 times higher in smooth muscle cells (SMCs) from human mammary artery (h-MA) vs. saphenous vein (h-SV). In endothelial cells (ECs), CRP3/MLP was scarcely detected in either h-MA or h-SV. Using an ex vivo flow through system that mimics arterial condition, we observed induction of CRP3/MLP expression in arterialized h-SV. Interestingly, the upregulation of CRP3/MLP was primarily dependent on stretch stimulus in SMCs, rather than shear stress in ECs. Finally, using a rat vein in vivo arterialization model, early (1-14 days) CRP3/MLP immunostaining was observed predominantly in the inner layer and later (28-90 days) it appeared more scattered in the vessel layers.

CONCLUSION

Here we provide evidence that CRP3/MLP is primarily expressed in arterial SMCs and that stretch is the main stimulus for CRP3/MLP induction in veins exposed to arterial haemodynamic conditions.

Defining the transcriptomic and proteomic profiles of rat ageing skeletal muscle by the use of a cDNA array, 2D- and Blue native-PAGE approach

We defined the transcriptomic and proteomic profiles of rat ageing skeletal muscle using a combined cDNA array, 2D- and Blue native-PAGE approach. This was allowed to obtain an overview of the interrelated events leading to the transcriptome/proteome/mitoproteome changes likely to underlie the structural/metabolic features of aged skeletal muscle. The main differences were found in genes/proteins related to energy metabolism, mitochondrial pathways, myofibrillar filaments, and detoxification. Concerning the abundance of mitochondrial OXPHOS complexes as well as their supramolecular organization and activity, mitochondria from old rats, when compared with those from young rats, contained significantly lower amounts of complex I (NADH:ubiquinone oxidoreductase), V (FoF1-ATP synthase), and III (ubiquinol:cytochrome c oxidoreductase). The same mitochondria contained a significantly larger amount of complex II (succinate:ubiquinone oxidoreductase), but an unchanged amount of complex IV (cytochrome c oxidase, COX). When comparing the supercomplex profiles between young and old muscle mitochondria, the densitometric analysis revealed that lighter supercomplexes were significantly reduced in older mitochondria, and that in the older group the major supercomplex bands were those representing heavier supercomplexes, likely suggesting a compensatory mechanism that, in ageing muscle, is functionally directed towards substrate channeling and catalytic enhancement advantaging the respirosome.

Structure and dynamics of the human muscle LIM protein

The family of cysteine rich proteins (CRP) comprises three closely homologous members that have been reported to interact with alpha-actinin. Muscular LIM protein (MLP/CRP3), the skeletal muscle variant, was originally discovered as a positive regulator of myogenesis and is suggested to be part of the stretch sensor of the myofibril through its interaction with telethonin (T-Cap). We determined the structure of both LIM domains of human MLP by nuclear magnetic resonance spectroscopy. We confirm by (15)N relaxation measurements that both LIM domains act as independent units and that the adjacent linker regions are fully flexible. With the published structures of CRP1 and CRP2, the complete family has now been structurally characterized.

Targeted disruption of the mouse Csrp2 gene encoding the cysteine- and glycine-rich LIM domain protein CRP2 result in subtle alteration of cardiac ultrastructure

Background

The cysteine and glycine rich protein 2 (CRP2) encoded by the Csrp2 gene is a LIM domain protein expressed in the vascular system, particularly in smooth muscle cells. It exhibits a bimodal subcellular distribution, accumulating at actin-based filaments in the cytosol and in the nucleus. In order to analyze the function of CRP2 in vivo, we disrupted the Csrp2 gene in mice and analysed the resulting phenotype.

Results

A ~17.3 kbp fragment of the murine Csrp2 gene containing exon 3 through 6 was isolated. Using this construct we confirmed the recently determined chromosomal localization (Chromosome 10, best fit location between markers D10Mit203 proximal and D10Mit150 central). A gene disruption cassette was cloned into exon 4 and a mouse strain lacking functional Csrp2 was generated. Mice lacking CRP2 are viable and fertile and have no obvious deficits in reproduction and survival. However, detailed histological and electron microscopic studies reveal that CRP2-deficient mice have subtle alterations in their cardiac ultrastructure. In these mice, the cardiomyocytes display a slight increase in their thickness, indicating moderate hypertrophy at the cellular level. Although the expression of several intercalated disc-associated proteins such as β-catenin, N-RAP and connexin-43 were not affected in these mice, the distribution of respective proteins was changed within heart tissue.

Conclusion

We conclude that the lack of CRP2 is associated with alterations in cardiomyocyte thickness and hypertrophy.

Sp6 downregulation of follistatin gene expression in ameloblasts

Sp6 is a member of the Sp family of transcription factors that regulate a wide range of cellular functions, such as cell growth and differentiation. Sp6, also called epiprofin, is specifically expressed in tooth germ, limb bud, and hair follicle, but there is little information on its function.To investigate the possible role of Sp6 in tooth development, first we established an Sp6-overproducing clone, CHA9, and analyzed the features of the cell, including cell proliferation and gene expression. The parental cells of CHA9 are the ameloblast-lineage G5 cells that we previously established from rat dental epithelia of lower incisor. Sp6 overproduction accelerated cell proliferation and induced the expression of ameloblastin mRNA, a marker of ameloblast differentiation. Second, we performed genome-wide screening of Sp6 target genes by microarray analysis. Out of a total 20,450 genes, 448 genes were up-regulated and 500 genes were down-regulated by Sp6. We found the expression of follistatin, a BMP antagonist, to be 22.4-fold lower in CHA9 than in control cells. Transfection of the Sp6-antisense construct into CHA9 cells restored follistatin expression back to equivalent levels seen in control cells, indicating that Sp6 regulates follistatin gene expression in ameloblasts. Our findings demonstrate that the follistatin gene is one of the Sp6 target genes in ameloblasts and suggest that Sp6 promotes amelogenesis through inhibition of follistatin gene expression.

Generation and characterization of Csrp1 enhancer-driven tissue-restricted Cre-recombinase mice

Cell type-specific genetic modification using the LoxP/Cre system is a powerful tool for genetic analysis of distinct cell lineages. Because of the unique arterial smooth muscle-restricted expression of a 5.0 kb cysteine-rich protein (Csrp1) enhancer (Lilly et al.,2001, Dev Biol 240:531-547), we hypothesized that a transgenic Cre line would prove useful for the smooth muscle lineage-specific genetic manipulation. Here we describe a transgenic mouse line, ECsrp1(Cre), where Cre is initially specifically expressed in arterial smooth muscle cells. Use of the ROSA26R reporter allele confirmed that Cre-mediated recombination in vascular smooth muscle cells began at approximately E10.0 and was highly proficient. Subsequently, Cre is expressed in restricted skeletal and nonvascular smooth muscle lineages. This lineage tracing data is important for future conditional knockout studies to understand where and when Cre-mediated deletion occurs and where Cre-expressing daughter cells finally localize. Additionally, we crossed the ECsrp1(Cre) mice to the ROSA26(-eGFP-DTA) diphtheria toxin A-expressing mice to genetically ablate ECsrp1(Cre) expressing cells. This ECsrp1(Cre) transgenic line should thus prove useful for genetic analysis of diverse aspects of cardiovascular morphogenesis and as a general smooth muscle lineage deletor line.

Transforming growth factor beta up-regulates cysteine-rich protein 2 in vascular smooth muscle cells via activating transcription factor 2

CRP2 (cysteine-rich protein) is a vascular smooth muscle cell (VSMC)-expressed LIM-only protein. CRP2 associates with the actin cytoskeleton and interacts with transcription factors in the nucleus to mediate smooth muscle cell gene expression. Using Csrp2 (gene symbol of the mouse CRP2 gene)-deficient mice, we previously demonstrated that an absence of CRP2 enhances VSMC migration and increases neointima formation following arterial injury. Despite its importance in vascular injury, the molecular mechanisms controlling CRP2 expression in VSMC are largely unknown. Transforming growth factor beta (TGFbeta), a key factor present in the vessel wall in the early phases of arterial response to injury, plays an important role in modulating lesion formation. Because both CRP2 and TGFbeta are mediators of VSMC responses, we examined the possibility that TGFbeta might regulate CRP2 expression. TGFbeta significantly induced CRP2 mRNA and protein expression in VSMCs. Promoter analysis identified a conserved cAMP-responsive element (CRE)-like site (TAACGTCA) in the Csrp2 promoter that was critical for basal promoter activity and response to TGFbeta. Gel mobility shift assays revealed that mainly ATF2 bound to this CRE-like element, and mutation of the CRE sequences abolished binding. TGFbeta enhanced the activation of ATF2, leading to increased phospho-ATF2 levels within the DNA-protein complexes. Furthermore, ATF2-transactivated Csrp2 promoter activity and TGFbeta enhanced this activation. In addition, a phosphorylation-negative ATF2 mutant construct decreased basal and TGFbeta-mediated Csrp2 promoter activity. Our results show for the first time in VSMC that TGFbeta activates ATF2 phosphorylation and Csrp2 gene expression via a CRE promoter element.

Cysteine-rich protein 2, a novel downstream effector of cGMP/cGMP-dependent protein kinase I-mediated persistent inflammatory pain

The cGMP/cGMP-dependent protein kinase I (cGKI) signaling pathway plays an important role in spinal nociceptive processing. However, downstream targets of cGKI in this context have not been identified to date. Using a yeast two-hybrid screen, we isolated cysteine-rich protein 2 (CRP2) as a novel cGKI interactor in the spinal cord. CRP2 is expressed in laminas I and II of the mouse spinal cord and is colocalized with cGKI, calcitonin gene-related peptide, and isolectin B4. Moreover, the majority of CRP2 mRNA-positive dorsal root ganglion (DRG) neurons express cGKI and peripherin. CRP2 is phosphorylated in a cGMP-dependent manner, and its expression increases in the spinal cord and in DRGs after noxious stimulation of a hindpaw. To elucidate the functional role of CRP2 in nociception, we analyzed mice with a targeted deletion of CRP2. CRP2-deficient (CRP2-/-) mice demonstrate normal behavioral responses to acute nociception and after axonal injury of the sciatic nerve, but increased nociceptive behavior in models of inflammatory hyperalgesia compared with wild-type mice. Intrathecal administration of cGMP analogs increases the nociceptive behavior in wild-type but not in CRP2-/- mice, indicating that the presence of CRP2 is important for cGMP-mediated nociception. These data suggest that CRP2 is a new downstream effector of cGKI-mediated spinal nociceptive processing and point to an inhibitory role of CRP2 in the generation of inflammatory pain.

Cytoskeleton-interacting LIM-domain protein CRP1 suppresses cell proliferation and protects from stress-induced cell death

Members of the cysteine-rich protein (CRP) family are actin cytoskeleton-interacting LIM-domain proteins known to act in muscle cell differentiation. We have earlier found that CRP1, a founding member of this family, is transcriptionally induced by UV radiation in human diploid fibroblasts [M. Gentile, L. Latonen, M. Laiho, Cell cycle arrest and apoptosis provoked by UV radiation-induced DNA damage are transcriptionally highly divergent responses, Nucleic Acids Res. 31 (2003) 4779-4790]. Here we show that CRP1 is induced by growth-inhibitory signals, such as increased cellular density, and cytotoxic stress induced by UV radiation or staurosporine. We found that high levels of CRP1 correlate with differentiation-associated morphology towards the myofibroblast lineage and that expression of ectopic CRP1 suppresses cell proliferation. Following UV- and staurosporine-induced stresses, expression of CRP1 provides a survival advantage evidenced by decreased cellular death and increased cellular metabolic activity and attachment. Our studies identify that CRP1 is a novel stress response factor, and provide evidence for its growth-inhibitory and cytoprotective functions.

Csrp1 regulates dynamic cell movements of the mesendoderm and cardiac mesoderm through interactions with Dishevelled and Diversin

Zebrafish Csrp1 is a member of the cysteine- and glycine-rich protein (CSRP) family and is expressed in the mesendoderm and its derivatives. Csrp1 interacts with Dishevelled 2 (Dvl2) and Diversin (Div), which control cell morphology and other dynamic cell behaviors via the noncanonical Wnt and JNK pathways. When csrp1 message is knocked down, abnormal convergent extension cell movement is induced, resulting in severe deformities in midline structures. In addition, cardiac bifida is induced as a consequence of defects in cardiac mesoderm cell migration. Our data highlight Csrp1 as a key molecule of the noncanonical Wnt pathway, which orchestrates cell behaviors during dynamic morphogenetic movements of tissues and organs.

Reversal of calcium cycling defects in advanced heart failure toward molecular therapy

Heart failure is a growing major cause of human morbidity and mortality worldwide. A wave of new insights from diverse laboratories has begun to uncover new therapeutic strategies that affect the molecular pathways within cardiomyocytes that drive heart failure progression. Using an integrative approach that employs insights from genetic-based studies in mouse and humans and in vivo somatic gene transfer studies, we have uncovered a new link between stress signals mediated by mechanical stretch and defects in sarcoplasmic reticulum (SR) calcium cycling. An intrinsic mechanical stress sensing system is embedded in the Z disc of cardiomyocytes, and defects in stretch responses can lead to heart failure progression and associated increases in wall stress. Reversal of the chronic increases in wall stress by promoting SR calcium cycling can prevent and partially reverse heart failure progression in multiple genetic and acquired model systems of heart failure in both small and large animals. We propose that reversal of advanced heart failure is possible by targeting the defects in SR calcium cycling, which may be a final common pathway for the progression of many forms of heart failure.

The expression of CSRP2 encoding the LIM domain protein CRP2 is mediated by TGF-β in smooth muscle and hepatic stellate cells

Transforming growth factor-beta (TGF-beta) is a cytokine implicated in differentiation of smooth muscle cells and other mesenchymal-derived cells. During hepatic fibrogenesis, TGF-beta has a pivotal role in the initiation, promotion, and progression of transdifferentiation of hepatic stellate cells into myofibroblasts that play a central role in the synthesis of extracellular matrix components. Both, smooth muscle and activated hepatic stellate cells, express smooth muscle alpha-actin, the calponin-related protein SM22alpha, and CSRP2 encoding the cysteine- and glycine-rich LIM domain protein 2 (CRP2). The aim of the present study was to determine whether the expression of CSRP2 is influenced by TGF-beta. Stimulation as well as sequestering experiments demonstrated that TGF-beta markedly influences CSRP2 gene activity. Inhibition experiments using the ALK5 inhibitor SB-431542 further reveal that the transcriptional stimulation of the CSRP2 gene is mediated via the ALK5/Smad2/Smad3 signalling pathway. By use of bisulfite genomic analysis of CpG islands within the 5' regulatory regions we could exclude methylation-associated silencing, previously found to be responsible for the transcriptional inactivity of CSRP2 in a variety of human cancer cells and in a multistage carcinogenesis model, as a cause for CSRP2 inactivity in hepatocytes or fully transdifferentiated myofibroblasts.

Cysteine-rich protein 1 (CRP1) regulates actin filament bundling

BACKGROUND

Cysteine-rich protein 1 (CRP1) is a LIM domain containing protein localized to the nucleus and the actin cytoskeleton. CRP1 has been demonstrated to bind the actin-bundling protein alpha-actinin and proposed to modulate the actin cytoskeleton; however, specific regulatory mechanisms have not been identified.

RESULTS

CRP1 expression increased actin bundling in rat embryonic fibroblasts. Although CRP1 did not affect the bundling activity of alpha-actinin, CRP1 was found to stabilize the interaction of alpha-actinin with actin bundles and to directly bundle actin microfilaments. Using confocal and photobleaching fluorescence resonance energy transfer (FRET) microscopy, we demonstrate that there are two populations of CRP1 localized along actin stress fibers, one associated through interaction with alpha-actinin and one that appears to bind the actin filaments directly. Consistent with a role in regulating actin filament cross-linking, CRP1 also localized to the membrane ruffles of spreading and PDGF treated fibroblasts.

CONCLUSION

CRP1 regulates actin filament bundling by directly cross-linking actin filaments and stabilizing the interaction of alpha-actinin with actin filament bundles.

Increased neointima formation in cysteine-rich protein 2-deficient mice in response to vascular injury

In response to arterial injury, medial vascular smooth muscle cells (VSMCs) proliferate and migrate into the intima, contributing to the development of occlusive vascular disease. The LIM protein cysteine-rich protein (CRP) 2 associates with the actin cytoskeleton and may maintain the cytoarchitecture. CRP2 also interacts with transcription factors in the nucleus to mediate SMC gene expression. To test the hypothesis that CRP2 may be an important regulator of vascular development or function we generated Csrp2 (gene symbol of the mouse CRP2 gene)-deficient (Csrp2(-/-)) mice by targeted mutation. Csrp2(-/-) mice did not have any gross vascular defects or altered expression levels of SM alpha-actin, SM22alpha, or calponin. Following femoral artery injury, CRP2 expression persisted in the vessel wall at 4 days and then decreased by 14 days. Intimal thickening was enhanced 3.4-fold in Csrp2(-/-) compared with wild-type (WT) mice 14 days following injury. Cellular proliferation was similar between WT and Csrp2(-/-) VSMC both in vivo and in vitro. Interestingly, Csrp2(-/-) VSMC migrated more rapidly in response to PDGF-BB and had increased Rac1 activation. Our data demonstrate that CRP2 is not required for vascular development. However, an absence of CRP2 enhanced VSMC migration and increased neointima formation following arterial injury.

p38 MAP kinase inhibition enables proliferation of adult mammalian cardiomyocytes

Adult mammalian cardiomyocytes are considered terminally differentiated and incapable of proliferation. Consequently, acutely injured mammalian hearts do not regenerate, they scar. Here, we show that adult mammalian cardiomyocytes can divide. One important mechanism used by mammalian cardiomyocytes to control cell cycle is p38 MAP kinase activity. p38 regulates expression of genes required for mitosis in cardiomyocytes, including cyclin A and cyclin B. p38 activity is inversely correlated with cardiac growth during development, and its overexpression blocks fetal cardiomyocyte proliferation. Activation of p38 in vivo by MKK3bE reduces BrdU incorporation in fetal cardiomyocytes by 17.6%. In contrast, cardiac-specific p38alpha knockout mice show a 92.3% increase in neonatal cardiomyocyte mitoses. Furthermore, inhibition of p38 in adult cardiomyocytes promotes cytokinesis. Finally, mitosis in adult cardiomyocytes is associated with transient dedifferentiation of the contractile apparatus. Our findings establish p38 as a key negative regulator of cardiomyocyte proliferation and indicate that adult cardiomyocytes can divide.

Transcripts from a human primordial follicle cDNA library

BACKGROUND

Human primordial follicles (PFs) or the oocyte-pre-granulosa complex, constitute the earliest and most immature stage of human oogenesis. The factors, signalling networks and the precise role of the oocyte and the pre-granulosa cells in initiating growth and recruitment from this finite resting pool remain largely unknown at present.

METHODS

To obtain a gene resource of this oogenesis stage and thereby determine a molecular blueprint of the human PF, a cDNA library was constructed from 50 isolated human PFs using the phagemid vector pTriplEx2.

RESULTS

Sequence analysis showed that 46.67% of these clones corresponded to known genes while 29.48% were uncharacterized genes that included hypothetical proteins, human cDNA clones and novel genes. Bioinformatics analysis revealed a preponderance of mitochondrial genes and repeat elements followed by ribosomal proteins, transcription and translation genes. Transcripts for heat shock proteins, cell cycle, embryogenesis genes and apoptosis genes were identified. Members of the ubiquitin-proteasome pathway, MAPK, p38/JNK, GPCR, Wnt, NF-kappaB and notch signalling pathways were identified. A mitochondrial pathway and a transcription factor pathway in the human PF were generated. The gene networks in the transcription factor pathway provided a first glimpse of the balance between proliferation and cell death/apoptosis in this earliest stage of oogenesis.

CONCLUSIONS

The abundance and diversity of retroviral elements and transcriptional repressor genes in the human PF suggest these could contribute to the maintainance of this oogenesis stage. The role of these genes in initial recruitment and in subsequent oogenesis stages will be greatly facilitated and elucidated by printing a human PF cDNA array of the sequenced clones and using it for gene profiling.

Combined cDNA array/RT‐PCR analysis of gene expression profile in rat gastrocnemius muscle: relation to its adaptive function in energy metabolism during fasting

We evaluated the effects of fasting on the gene expression profile in rat gastrocnemius muscle using a combined cDNA array and RT-PCR approach. Of the 1176 distinct rat genes analyzed on the cDNA array, 114 were up-regulated more than twofold in response to fasting, including all 17 genes related to lipid metabolism present on the membranes and all 10 analyzed components of the proteasome machinery. Only 7 genes were down-regulated more than twofold. On the basis of our analysis of genes on the cDNA array plus the data from our RT-PCR assays, the metabolic adaptations shown by rat gastrocnemius muscle during fasting are reflected by i) increased transcription both of myosin heavy chain (MHC) Ib (associated with type I fibers) and of at least three factors involved in the shift toward type I fibers [p27kip1, muscle LIM protein (MLP), cystein rich protein-2], of which one (MLP) has been shown to enhance the activity of MyoD, which would explain the known increase in the expression of skeletal muscle uncoupling protein-3 (UCP3); ii) increased lipoprotein lipase (LPL) expression, known to trigger UCP3 transcription, which tends, together with the first point, to underline the suggested role of UCP3 in mitochondrial lipid handling (the variations under the first point and this one have not been observed in mice, indicating a species-specific regulation of these mechanisms); iii) reduced expression of the muscle-specific coenzyme Q (CoQ)7 gene, which is necessary for mitochondrial CoQ synthesis, together with an increased expression of mitochondrial adenylate kinase 3, which inactivates the resident key enzyme for CoQ synthesis, 3-hydroxy-3-methylglutaryl CoA reductase (HMGR), the mRNA level for which fell during fasting; and iv) increased transcription of components of the proteasomal pathways involved in protein degradation/turnover.

Identification of a CArG-independent region of the cysteine-rich protein 2 promoter that directs expression in the developing vasculature

Cysteine-rich protein (CRP)2 is a member of the LIM-only CRP family that is expressed in vascular smooth muscle cells (VSMC). To gain insight into the transcription of CSRP2 (gene name for CRP2) in VSMC, we analyzed the 5'-flanking sequence of the CSRP2 gene. We showed previously that 4,855 bp of the 5'-flanking sequence of the CSRP2 gene directed lacZ reporter gene expression, primarily in the VSMC of transgenic mice. To further define the regulatory sequences important for CSRP2 expression in VSMC, a series of promoter constructs containing deletions of the 5'-flanking sequence upstream of a nuclear-localized lacZ reporter gene were generated and analyzed. Similar to that observed in the -4855CSRP2-lacZ mice, beta-galactosidase reporter activity was detected in the developing great vessels, aorta, intersegmental arteries, umbilical vessels, endocardial cushions, and neural tube in the -3513-, -2663-, -795-, and -664CSRP2-lacZ lines. However, an internal deletion of bp -573 to -550 abolished the vascular, but not the neural tube, staining. Interestingly, no CArG box [CC(A/T)6GG] was present in the -795-bp fragment. Cotransfection experiments showed that dominant-negative serum response factor (SRF) did not repress CSRP2 promoter activity, which was different from the repressive effect of dominant-negative SRF on the SM22 alpha promoter. Our data suggest the presence of a VSMC-specific element(s) within bp -573 to -550 of the CSRP2 5'-flanking sequence; however, in contrast to many other smooth muscle genes, transcriptional regulation of the CSRP2 gene is not dependent on SRF.

Mutations in the muscle LIM protein and alpha-actinin-2 genes in dilated cardiomyopathy and endocardial fibroelastosis

Dilated cardiomyopathy (DCM) is a major cause of morbidity and mortality. Two genes have been identified for the X-linked forms (dystrophin and tafazzin), while mutations in multiple genes cause autosomal dominant DCM. Muscle LIM protein (MLP) is a member of the cysteine-rich protein (CRP) family and has been implicated in both myogenesis and sarcomere assembly. In the latter role, it binds zyxin and alpha-actinin, both of which are involved in actin organization. An MLP-deficient mouse has been described; these mice develop dilated cardiomyopathy and heart failure. Based upon these data, and the recent descriptions of mutations in MLP in patients with DCM or hypertrophic cardiomyopathy, we screened patients for mutations in the MLP and alpha-actinin-2 genes. We identified a patient with DCM and EFE, having a mutation in MLP with the residue lysine 69 substituted by arginine (K69R). This is within a highly conserved region adjacent to the first LIM domain involved in alpha-actinin binding. Analysis in cell culture systems demonstrated that the mutation abolishes the interaction between MLP and alpha-actinin-2 and the cellular localization of MLP was altered. In another individual with DCM, a W4R mutation was identified. However, this mutation did not segregate with disease in this family. In another patient with DCM, a Q9R mutation was identified in alpha-actinin-2. This mutation also disrupted the interaction with MLP and appeared to inhibit alpha-actinin function in cultured cells, in respect to the nuclear localization of actinin and the initiation of cellular differentiation.

A novel IL-10 signalling mechanism regulates TIMP-1 expression in human prostate tumour cells

We have previously reported that interleukin 10 (IL-10) signalling stimulated activation of a specific enhancer element, termed HTE-1, to promote tissue inhibitor of matrix metalloproteinase1 (TIMP-1) expression in human bone metastatic PC-3 subclone (PC-3 ML) cells. Recently, we have identified an IL-10 responsive signal molecule, termed IL-10E1, which binds the HTE-1 element and cloned the gene encoding for the 22 kDa protein. In this paper, we have examined the mechanism of IL-10/IL-10 receptor signalling in two distinct human prostate cell lines, a 'normal' prostate epithelial cell line, termed NPTX-1532 and highly metastatic PC-3 ML tumour cells. Signalling cascade studies revealed that IL-10 stimulated tyrosine phosphorylation of JAK1 and TYK2 receptor kinases and tyrosine phosphorylation of IL-10E1. Phosphorylation, triggered IL-10E1's rapid translocation to the nucleus by 10-30 min. Deletion analysis combined with transient transfection experiments revealed that the n-terminal domain (approximately 74 a.a.) of the IL-10E1 protein, the nt-nls peptide, was stimulated by IL-10 to translocate to the nucleus and induce TIMP-1 expression. Site-directed mutagenesis further showed that phosphorylation of two tyrosine moieties (Y57 and Y62) of the nt-nls peptide was required for IL-10 activation of signalling and TIMP-1 expression. The data demonstrate, for the first time, that IL-10 receptor signalling of TIMP-1 expression is regulated by tyrosine phosphorylation of a novel gene, IL-10E1, in human prostate cells.

ALP and MLP distribution during myofibrillogenesis in cultured cardiomyocytes

The Z-line is a multifunctional macromolecular complex that anchors sarcomeric actin filaments, mediates interactions with intermediate filaments and costameres, and recruits signaling molecules. Antiparallel alpha-actinin homodimers, present at Z-lines, cross-link overlapping actin filaments and also bind other cytoskeletal and signaling elements. Two LIM domain containing proteins, alpha-actinin associated LIM protein (ALP) and muscle LIM protein (MLP), interact with alpha-actinin, distribute in vivo to Z-lines or costameres, respectively, and, when absent, are associated with heart disease. Here we describe the behavior of ALP and MLP during myofibrillogenesis in cultured embryonic chick cardiomyocytes. As myofibrils develop, ALP and MLP are observed in distinct distribution patterns in the cell. ALP is coincident with alpha-actinin from the first stage of myofibrillogenesis and co-distributes with alpha-actinin to Z-lines and intercalated discs in mature myofibrils. Interestingly, we also demonstrate using ALP-GFP transfection experiments and an in vitro binding assay that the ALP-alpha-actinin binding interaction is not required to target ALP to the Z-line. In contrast, MLP localization is not co-incident with that of alpha-actinin until late stages of myofibrillogenesis; however, it is present in premyofibrils and nascent myofibrils prior to the incorporation of other costameric components such as vinculin, vimentin, or desmin. Our observations support the view that ALP function is required specifically at actin anchorage sites. The subcellular distribution pattern of MLP during myofibrillogenesis suggests that it functions during differentiation prior to the establishment of costameres.

Cysteine-rich LIM-only proteins CRP1 and CRP2 are potent smooth muscle differentiation cofactors

Cysteine-rich LIM-only proteins, CRP1 and CRP2, expressed during cardiovascular development act as bridging molecules that associate with serum response factor and GATA proteins. SRF-CRP-GATA complexes strongly activated smooth muscle gene targets. CRP2 was found in the nucleus during early stages of coronary smooth muscle differentiation from proepicardial cells. A dominant-negative CRP2 mutant blocked proepicardial cells from differentiating into smooth muscle cells. Together with SRF and GATA proteins, CRP1 and CRP2 converted pluripotent 10T1/2 fibroblasts into smooth muscle cells, while muscle LIM protein CRP3 inhibited the conversion. Thus, LIM-only proteins of the CRP family play important roles in organizing multiprotein complexes, both in the cytoplasm, where they participate in cytoskeletal remodeling, and in the nucleus, where they strongly facilitate smooth muscle differentiation.