Upregulation of Hic-5 in glomerulosclerosis and its regulation of mesangial cell apoptosis.

Glomerulosclerosis is characterized by the loss of glomerular cells by apoptosis and deposition of collagen type I into the normal collagen IV-containing mesangial matrix. We sought to determine the alterations that might contribute to these changes by performing proteomic analysis of rat mesangial cell lysates comparing cells cultured on normal collagen type IV to those grown on abnormal collagen type I surfaces. Subculture on collagen type I was associated with changed expression of several proteins, including a significant upregulation of the paxillin-like LIM protein, hydrogen-peroxide-induced clone 5 (Hic-5), and increased the susceptibility of the cells to apoptosis in response to physiological triggers. When we knocked down Hic-5 (using siRNA), we found mesangial cells grown on collagen type I were protected from apoptosis to the same degree as untreated cells grown on collagen type IV. Further we found that the level of Hic-5 in vivo was almost undetectable in control rats but increased dramatically in the glomerular mesangium of remnant kidneys 90 and 120 days after subtotal nephrectomy. This induction of Hic-5 paralleled the upregulation of mesangial collagen type I expression and glomerular cell apoptosis. Our results suggest that Hic-5 is pivotal in mediating the response of mesangial cells to attachment on abnormal extracellular matrix during glomerular scarring.

The application of proteomics technology to thrombosis research: the identification of potential therapeutic targets in cardiovascular disease.

Thrombus formation underpins the development of cardiovascular diseases, including acute coronary syndromes and ischaemic stroke. A number of well-characterised cardiovascular risk factors which contribute to the development of the majority of cardiovascular events have been identified, including dyslipidaemia, hypertension and diabetes. Individuals with type 2 diabetes mellitus (T2DM) have a 3- to 5-fold increased risk for development of cardiovascular disease (CVD). They may have a cluster of haemostatic abnormalities, including elevated levels of plasminogen activator inhibitor-1 (PAI-1) and fibrinogen, which contribute to acute thrombotic events. It is clear that additional unidentified risk factors contribute to the pathogenesis of cardiovascular events, and so the search for novel biomarkers and effectors, particularly in individuals with T2DM, remains a major challenge of cardiovascular medicine. Plasma and cellular proteins which contribute to thrombus formation have the potential to confer a pro-thrombotic state and represent a link between genotype, environment and disease phenotype. The comprehensive analysis of these proteins is now increasingly facilitated through the continued development of proteomic technologies which provide multifaceted approaches to the identification of novel biomarkers and/or effectors of thrombus formation and on which future anticoagulant and thrombolytic therapies may be based. This review provides an overview of current proteomic technologies. It focuses on the recent studies in which these technologies have been applied in the search for novel proteins that may confer increased risk of acute cardiovascular diseases and therefore that may influence disease progression and therapy.

Proteomic identification of Drosophila melanogaster male accessory gland proteins, including a pro-cathepsin and a soluble gamma-glutamyl transpeptidase.

BACKGROUND: In Drosophila melanogaster, the male seminal fluid contains proteins that are important for reproductive success. Many of these proteins are synthesised by the male accessory glands and are secreted into the accessory gland lumen, where they are stored until required. Previous studies on the identification of Drosophila accessory gland products have largely focused on characterisation of male-specific accessory gland cDNAs from D. melanogaster and, more recently, Drosophila simulans. In the present study, we have used a proteomics approach without any sex bias to identify proteins in D. melanogaster accessory gland secretions. RESULTS: Thirteen secreted accessory gland proteins, including seven new accessory gland proteins, were identified by 2D-gel electrophoresis combined with mass spectrometry of tryptic fragments. They included protein-folding and stress-response proteins, a hormone, a lipase, a serpin, a cysteine-rich protein and two peptidases, a pro-enzyme form of a cathepsin K-like cysteine peptidase and a gamma-glutamyl transpeptidase. Enzymatic studies established that accessory gland secretions contain a cysteine peptidase zymogen that can be activated at low pH. This peptidase may have a role in the processing of female and other male-derived proteins, but is unlikely to be involved in the processing of the sex peptide. gamma-Glutamyl transpeptidases are type II integral membrane proteins; however, the identified AG gamma-glutamyl transpeptidase (GGT-1) is unusual in that it is predicted to be a soluble secreted protein, a prediction that is supported by biochemical evidence. GGT-1 is possibly involved in maintaining a protective redox environment for sperm. The strong gamma-glutamyl transpeptidase activity found in the secretions provides an explanation for the observation that glutamic acid is the most abundant free amino acid in accessory gland secretions of D. melanogaster. CONCLUSION: We have applied biochemical approaches, not used previously, to characterise prominent D. melanogaster accessory gland products. Of the thirteen accessory gland secreted proteins reported in this study, six were represented in a D. simulans male accessory gland EST library that was biased for male-specific genes. Therefore, the present study has identified seven new secreted accessory gland proteins, including GGT-1, which was not recognised previously as a secreted accessory gland product.

The identification of nucleic acid-interacting proteins using a simple proteomics-based approach that directly incorporates the electrophoretic mobility shift assay.

Proteins that interact with nucleic acids are central to numerous cellular processes, and their continuing characterization represents one of the foremost challenges in the postgenomic era. Here we describe a simple proteomics-based approach for the identification by mass spectrometry of proteins in crude extracts that interact with nucleic acids. It incorporates the electrophoretic mobility shift assay and is based on the finding that when a protein forms a complex with nucleic acid its electrophoretic mobility is affected as well as that of the nucleic acid. Our method should greatly reduce and in some cases may even eliminate the need for extensive protein purification and as such should contribute significantly to the functional annotation of the proteome. Furthermore it requires no prior knowledge of the molecular mass, quaternary structure, or pI of the interacting protein. Proof of principle is demonstrated using a recently discovered transcription factor; however, the approach should also have application in the identification of proteins that interact with RNA.

cDNAs encoding large venom proteins from the parasitoid wasp Pimpla hypochondriaca identified by random sequence analysis.

Venom from the parasitoid wasp Pimpla hypochondriaca contains numerous proteins, has potent in vitro anti-haemocytic properties, and disrupts host encapsulation responses. By sequencing 500 cDNAs randomly isolated from a venom gland library, we have identified 60 clones that encode proteins containing potential secretory signal sequences. To identify cDNAs encoding particular venom proteins, N-terminal amino acid sequences were determined for large (>30 kDa) venom proteins that had been separated using a combination of gel filtration and SDS-PAGE. We describe five of these cDNAs, which encoded residues that matched with the N-terminal sequences of previously undescribed venom proteins. cDNAs vpr1 and vpr3 encoded related proteins of approximately 32 kDa that were found in widely different fractions of gel filtration-separated venom. Neither vpr1 nor vpr3 were closely related to any other protein in the GenBank database, suggesting that they are highly specialised venom components. vpr2 encoded a 57-kDa polypeptide that was similar to a Drosophila protein, of unknown function, which lacks a signal sequence. A fourth clone, tre1, encoded a 61-kDa protein with extensive sequence similarity to trehalases. The 76-kDa sequence encoded by lac1 contained three regions which were very similar to histidine-rich copper-binding motifs, and could be aligned with the laccase from the fungus Coprinus cinereus. This study represents a significant step towards a holistic view of the molecular composition of a parasitoid wasp venom.

Ghrelin can bind to a species of high density lipoprotein associated with paraoxonase.

Ghrelin is a 28-residue peptide hormone that is principally released from the stomach during fasting and prior to eating. Two forms are present in human plasma: the unmodified peptide and a less abundant acylated version, in which octanoic acid is attached to the third residue, a serine, via an ester linkage. The acylated form of ghrelin acts as a ligand for the growth hormone secretagogue receptor and can stimulate the release of growth hormone from the pituitary gland. It also initiates behavioral and metabolic adaptations to fasting. Here we show that an immobilized form of ghrelin specifically binds a species of high density lipoprotein associated with the plasma esterase, paraoxonase, and clusterin. Both free ghrelin and paraoxon, a substrate for paraoxonase, can inhibit this interaction. An endogenous species of ghrelin is found to co-purify with high density lipoprotein during density gradient centrifugation and subsequent gel filtration. This interaction links the orexigenic peptide hormone ghrelin to lipid transport and metabolism. Furthermore, the interaction of the esterified hormone ghrelin with a species of HDL containing an esterase suggests a possible mechanism for the conversion of ghrelin to des-acyl ghrelin.