Chromosomal assignment of three rat and human H-rev genes, putative tumor suppressors, down-regulated in malignantly HRAS-transformed cells

Actin cytoskeleton remodeling by the alternatively spliced isoform of PDLIM4/RIL protein

RIL (product of PDLIM4 gene) is an actin-associated protein that has previously been shown to stimulate actin bundling by interacting with actin-cross-linking protein α-actinin-1 and increasing its affinity to filamentous actin. Here, we report that the alternatively spliced isoform of RIL, denoted here as RILaltCterm, functions as a dominant-negative modulator of RIL-mediated actin reorganization. RILaltCterm is regulated at the level of protein stability, and this protein isoform accumulates particularly in response to oxidative stress. We show that the alternative C-terminal segment of RILaltCterm has a disordered structure that directs the protein to rapid degradation in the core 20 S proteasomes. Such degradation is ubiquitin-independent and can be blocked by binding to NAD(P)H quinone oxidoreductase NQO1, a detoxifying enzyme induced by prolonged exposure to oxidative stress. We show that either overexpression of RILaltCterm or its stabilization by stresses counteracts the effects produced by full-length RIL on organization of actin cytoskeleton and cell motility. Taken together, the data suggest a mechanism for fine-tuning actin cytoskeleton rearrangement in response to stresses.

ALP/Enigma PDZ-LIM domain proteins in the heart

Actinin-associated LIM protein (ALP) and Enigma are two subfamilies of Postsynaptic density 95, discs large and zonula occludens-1 (PDZ)-Lin-11, Isl1 and Mec-3 (LIM) domain containing proteins. ALP family members have one PDZ and one LIM domain, whereas Enigma proteins contain one PDZ and three LIM domains. Four ALP and three Enigma proteins have been identified in mammals, each having multiple splice variants and unique expression patterns. Functionally, these proteins bind through their PDZ domains to alpha-actinin and bind through their LIM domains or other internal protein interaction domains to other proteins, including signaling molecules. ALP and Enigma proteins have been implicated in cardiac and skeletal muscle structure, function and disease, neuronal function, bipolar disorder, tumor growth, platelet and epithelial cell motility and bone formation. This review will focus on recent advances in the biological roles of ALP/Enigma PDZ-LIM domain proteins in cardiac muscle and provide insights into mechanisms by which mutations in these proteins are related to human cardiac disease.

Characterization of interaction between CLP36 and palladin

CLP36 is a member of the PDZ-LIM family of proteins, which associates with alpha-actinin and localizes to the actin cytoskeleton. CLP36 is involved in the formation of stress fibers and focal adhesions; however, the molecular mechanism of how CLP36 regulates stress fiber formation is still unknown. To investigate the physiological function of CLP36, we performed yeast two-hybrid screening, and found that CLP36 interacts with palladin. Palladin is an important structural element of the actin cytoskeleton that is ubiquitously expressed and associates with alpha-actinin. The interaction was dependent on the PDZ domain of CLP36 and the C-terminus of palladin, and silencing of palladin suppressed localization of CLP36 to stress fibers. Overexpression of the PDZ domain of CLP36 also inhibited the localization of palladin to stress fibers, suggesting that the association of CLP36 and palladin is important for the localization of both proteins to stress fibers. Our experimental results indicate that alpha-actinin, CLP36 and palladin form a protein complex and contribute to regulation of the actin cytoskeleton.

Structural analysis and expression profile of a novel gene on chromosome 5q23 encoding a Golgi-associated protein with six splice variants, and involved within the 5q deletion of a Ph(-) CML patient

We have identified a novel gene, upstream of the cytokine gene cluster region in 5q23-31, residing within one of the most common deleted segments associated with MDS. The novel gene exhibits significant alternative splicing generating at least six splice variants encoding four putative proline-rich protein isoforms, one of which is Golgi-associated. The gene is ubiquitously expressed and conserved among species with the C. elegans homologue being the most interesting, since it resides within an operon with two other genes, phospholipase D and dishevelled, a member of the Wnt pathway, suggesting a functional association. In addition, the novel gene and other key regulatory genes of the region, such IL3, Ril, AF5q31 and TCF-1, were found to be deleted in an atypical CML case, thus underscoring the significance of this subregion in the leukemogenesis process.

Right ventricular hypertrophy secondary to pulmonary hypertension is linked to rat chromosome 17: evaluation of cardiac ryanodine Ryr2 receptor as a candidate

BACKGROUND

Fischer 344 (F344) rats are relatively resistant to hypoxia-induced right ventricular (RV) hypertrophy compared with the Wistar-Kyoto (WKY) strain. These 2 strains were used to examine the genetic basis for the differential response.

METHODS AND RESULTS

Male F(2) offspring from an F344xWKY intercross were exposed to hypoxia (10% O(2)) for 3 weeks, and pulmonary artery pressure and cardiac chamber weights were measured. Genomic DNA was screened by use of polymorphic microsatellite markers across the whole genome (excluding the sex chromosomes). A quantitative trait locus (QTL) for RV weight was identified on rat chromosome 17 (lod score 6.5) that accounted for 22% of the total variance of RV weight in the F(2) population and was independent of pulmonary artery pressure. The peak was centered over marker D17Rat41, close to Chrm3, with a 1-lod support interval of 5 cM. Comparison of homologous regions in mice and humans suggested that Ryr2, the cardiac isoform of the ryanodine receptor, colocalizes with our QTL. A panel of somatic cell hybrids and fluorescence in situ hybridization mapped Ryr2 close to the gene Chrm3 within our QTL. [(3)H]Ryanodine binding to cardiac membranes from the parental strains showed a 21% reduction in B(max) in the WKY compared with the F344 strain, with no difference in K:(d).

CONCLUSIONS

These data provide the first demonstration of a QTL linked to the RV response to hypoxia-induced pulmonary hypertension. The Ryr2 receptor gene lies within this QTL and merits further investigation as a candidate for this differential RV response.

Characterization and molecular cloning of rat C1qRp, a receptor on NK cells

Here we report the generation of monoclonal antibodies (mAb) LOV3 and LOV8 to a 110-130-kDa membrane glycoprotein expressed by rat NK cells. This NK surface molecule was identified by eucaryotic expression cloning as the structural orthologue of the phagocytosis-stimulating receptor for complement factor C1q and mannose-binding lectin on human macrophages, C1qRp. Rat C1qRp is a monomeric type I integral membrane protein consisting of 643 amino acids with an N-terminal lectin-like domain, five epidermal growth factor-like domains, a transmembrane domain and a 45-residue cytoplasmic domain. It is encoded by a single gene on rat chromosome 3q41-q42 and is 67% and 87.5% identical at the amino acid level to human and mouse C1qRp, respectively. Rat C1qRp is expressed by resting and by activated NK cells, on subpopulations of NKR-P1(+) T cells (NK/T cells), dendritic cells, macrophages and granulocytes, but not by B cells or NKR-P1(-) T cells. Expression of this innate immune receptor is therefore not restricted to hematopoietic cells of the myeloid lineage, but is also expressed on subsets of cells of lymphoid origin. The mAb did not affect the cytotoxic function of NK cells, and C1qRp on NK cells may have functions not related to NK killing.

Primary structure, tissue distribution, and chromosomal localization of a novel isoform of lysyl hydroxylase (lysyl hydroxylase 3)

We report characterization of a novel isoform of lysyl hydroxylase (lysyl hydroxylase 3, LH3). The cDNA clones encode a polypeptide of 738 amino acids, including a signal peptide. The amino acid sequence has a high overall identity with LH1 and LH2, the isoforms characterized earlier. Conserved regions are present in the carboxyl-terminal portion of the isoforms and also in the central part of the molecules. Histidine and asparagine residues, which are conserved in the other isoforms and are known to be required for enzymatic activity, are also conserved in the novel isoform. The gene for LH3 (PLOD3) has been assigned to human chromosome 7q36 and rat chromosome 12. Gene expression of LH3 is highly regulated in adult human tissues. A strong hybridization signal, corresponding to an mRNA 2.75 kilobases in size, is obtained in heart, placenta and pancreas on multiple tissue RNA blots. Expression of the cDNA in vitro results in the synthesis of a protein that hydroxylates lysyl residues in collagenous sequences in a non-triple helical conformation.

The human RIL gene: mapping to human chromosome 5q31.1, genomic organization and alternative transcripts

The ril gene encoding a LIM domain protein of an unknown function was previously identified by differential expression cloning as a candidate tumor suppressor gene in rat fibroblasts (Kiess, M., Scharm, B., Aguzzi, A., Hajnal, A., Klemenz, R., Schwarte-Waldhoff, I., Schafer, R., 1995. Expression of ril, a novel LIM domain gene, is down-regulated in HRAS-transformed cells and restored in phenotypic revertants. Oncogene 10, 61-68). Searching for novel genes on human chromosome 5q31.1 by the cDNA selection technique, we isolated a cDNA clone identical with the cDNA of the human RIL gene (GenBank Accession No. X93510). The human 5q31.1 region is of interest because it contains the cytokine gene cluster and is frequently deleted in the malignant cells of patients with myelodysplasia and myeloid leukemia. Using Southern blot analysis and restriction mapping of genomic YAC (yeast artificial chromosome) and cosmid clones, we located the human RIL gene 240-260 kb telomeric to the IRF1 gene and characterized its genomic structure. PCR analysis indicated the presence of two alternative RIL transcripts in human fetal brain mRNA. The major transcript is identical with the RIL cDNA previously deposited in GenBank and contains seven exons distributed over 14.5 kb of genomic DNA with the two last 3'-exons coding a LIM domain. The minor transcript lacks the sixth exon compared with the major transcript, which leads to the loss of the LIM domain. We also identified two putative transcription start points (tsp) and sequenced the 5'-flanking region of RIL to reveal potential binding sites for transcriptional factors.