Identification of diagnostic upper gastrointestinal cancer tissue type-specific urinary biomarkers.

Several potential urinary biomarkers exhibiting an association with upper gastrointestinal tumour growth have been previously identified, of which S100A6, S100A9, rabenosyn-5 and programmed cell death 6-interacting protein (PDCD6IP) were further validated and found to be upregulated in malignant tumours. The cancer cohort from our previous study was subclassified to assess whether distinct molecular markers can be identified for each individual cancer type using a similar approach. Urine samples from patients with cancers of the stomach, oesophagus, oesophagogastric junction or pancreas were analysed by surface-enhanced laser desorption/ionization-time-of-flight mass spectrometry using both CM10 and IMAC30 (Cu2+-complexed) chip types and LC-MS/MS-based mass spectrometry after chromatographic enrichment. This was followed by protein identification, pattern matching and validation by western blotting. We found 8 m/z peaks with statistical significance for the four cancer types investigated, of which m/z 2447 and 2577 were identified by pattern matching as fragments of cathepsin-B (CTSB) and cystatin-B (CSTB); both molecules are indicative of pancreatic cancer. Additionally, we observed a potential association of upregulated α-1-antichymotrypsin with pancreatic and gastric cancers, of PDCD6IP, vitelline membrane outer layer protein 1 homolog (VMO1) and triosephosphate isomerase (TPI1) with oesophagogastric junctional cancers, and of complement C4-A, prostatic acid phosphatase, azurocidin and histone-H1 with oesophageal cancer. Furthermore, the potential pancreatic cancer biomarkers CSTB and CTSB were validated independently by western blotting. Therefore, the present study identified two new potential urinary biomarkers that appear to be associated with pancreatic cancer. This may provide a simple, non-invasive screening test for use in the clinical setting.

Urinary peptidomics in a rodent model of diabetic nephropathy highlights epidermal growth factor as a biomarker for renal deterioration in patients with type 2 diabetes.

Many diabetic patients suffer from declining renal function without developing albuminuria. To identify alternative biomarkers for diabetic nephropathy (DN) we performed urinary peptidomic analysis in a rodent model in which hyperglycemia and hypertension synergize to promote renal pathologic changes consistent with human DN. We identified 297 increased and 15 decreased peptides in the urine of rats with DN compared with controls, including peptides derived from proteins associated with DN and novel candidate biomarkers. We confirmed by ELISA that one of the parent proteins, urinary epidermal growth factor (uEGF), was more than 2-fold reduced in rats with DN in comparison with controls. To assess the clinical utility of uEGF we examined renal outcomes in 642 participants from the Edinburgh Type 2 Diabetes Study who were normoalbuminuric and had preserved renal function at baseline. After adjustment for established renal risk factors, a lower uEGF to creatinine ratio was associated with new-onset estimated glomerular filtration rate less than 60 ml/min per 1.73m(2) (odds ratio 0.48; 95% confidence interval, 0.26-0.90), rapid (over 5% per annum) decline in renal function (odds ratio 0.44; 95% confidence interval, 0.27-0.72) or the composite of both outcomes (odds ratio 0.38; 95% confidence interval, 0.24-0.62). Thus, the utility of a low uEGF to creatinine ratio as a biomarker of progressive decline in renal function in normoalbuminuric patients should be assessed in additional populations.

Heat-shock protein 60 translocates to the surface of apoptotic cells and differentiated megakaryocytes and stimulates phagocytosis.

Heat-shock protein 60 (Hsp60) is a highly conserved stress protein which has chaperone functions in prokaryotes and mammalian cells. Hsp60 is associated with the mitochondria and the plasma membrane through phosphorylation by protein kinase A, and is incorporated into lipid membranes as a protein-folding chaperone. Its diverse intracellular chaperone functions include the secretion of proteins where it maintains the conformation of precursors and facilitates their translocation through the plasma membrane. We report here that Hsp60 is concentrated in apoptotic membrane blebs and translocates to the surface of cells undergoing apoptosis. Hsp60 is also enriched in platelets derived from terminally differentiated megakaryocytes and expressed at the surface of senescent platelets. Furthermore, the exposure of monocytic U937 cells to Hsp60 enhanced their phagocytic activity. Our results suggests that externalized Hsp60 in apoptotic cells and senescent platelets influences events subsequent to apoptosis, such as the clearance of apoptotic cells by phagocytes.

Mass spectrometric detection of candidate protein biomarkers of cancer cachexia in human urine.

Increased membrane permeability and myofibrillar protein breakdown are established features of cancer cachexia. Proteins released from cachectic muscle may be excreted in urine to act as biomarkers of the cachectic process. One-dimensional SDS polyacrylamide gel electrophoresis followed by matrix-assisted laser desorption/ionisation or liquid chromatography tandem mass spectrometry was used to compare the protein content of urine from cachectic (>10% weight loss) (n=8) and weight-stable (n=8) gastro-oesophageal cancer patients and healthy controls (n=8). Plasma creatine kinase concentration was used as a marker of gross muscle breakdown. The number of protein species identified in cachectic samples (median 42; range 28-61; total 199) was greater than that identified in weight-stable cancer (median 15; range 9-28; total 79) and control samples (median 12.5; range 5-18; total 49) (P<0.001). Many of the proteins identified have not been reported previously in the urine of cancer patients. Proteins identified specifically in cachectic samples included muscle (myosin species), cytoskeletal (alpha-spectrin; nischarin) and microtubule-associated proteins (microtubule-actin crosslinking factor; microtubule-associated protein-1B; bullous pemphigoid antigen 1), whereas immunoglobulin kappa-light chain and zinc alpha-2 glycoprotein appeared to represent markers of cancer. The presence of myosin in urine (without an increase in plasma creatine kinase) is consistent with a specific loss of myosin as part of the cachectic process. Urinary proteomics using mass spectrometry can identify muscle-specific and non-muscle-specific candidate biomarkers of cancer cachexia.

The identification of a reaction site of glutathione mixed-disulphide formation on gammaS-crystallin in human lens.

The glutathionylation of human lens proteins was examined by Western-blot analysis with an anti-GSH antibody and scanning. Several different glutathionylated proteins were observed, and a 47 kDa band was of particular interest. This band did not appear after SDS/PAGE under reducing conditions, suggesting that it was a glutathionylated fraction. The 47 kDa band was found principally in the outer part of the lens, the cortex, but not in the lens nucleus where older proteins are present. The 47 kDa component was composed of betaB1-, betaB2- and gammaS-crystallin, with the gammaS-crystallin having glutathione bound at Cys-82 and at Cys-22, Cys-24 or Cys-26. We conclude that when glutathione becomes bound to gammaS-crystallin, it causes it to bind in turn to the beta-crystallin polypeptides to form a dimer.

Assembly of EcoKI DNA methyltransferase requires the C-terminal region of the HsdM modification subunit.

The methyltransferase component of type I DNA restriction and modification systems comprises three subunits, one DNA sequence specificity subunit and two DNA modification subunits. Limited proteolysis of the EcoKI methyltransferase shows that a 55-kDa N-terminal fragment of the 59-kDa modification subunit is resistant to degradation. We have purified this fragment and determined by mass spectrometry that proteolysis removes 43 or 44 amino acids from the C-terminus. The fragment fails to interact with the other subunits even though it still possesses secondary and tertiary structure and the ability to bind the S-adenosylmethionine cofactor. We conclude that the C-terminal region of the modification subunit of EcoKI is essential for the assembly of the EcoKI methyltransferase.

Identification of N-acetylgalactosamine-containing glycoproteins PEB3 and CgpA in Campylobacter jejuni.

It was demonstrated recently that there is a system of general protein glycosylation in the human enteropathogen Campylobacter jejuni. To characterize such glycoproteins, we identified a lectin, Soybean agglutinin (SBA), which binds to multiple C. jejuni proteins on Western blots. Binding of lectin SBA was disrupted by mutagenesis of genes within the previously identified protein glycosylation locus. This lectin was used to purify putative glycoproteins selectively and, after sodium dodecyl sulphatepolyacrylamide gel electrophoresis (SDS-PAGE), Coomassie-stained bands were cut from the gels. The bands were digested with trypsin, and peptides were identified by mass spectrometry and database searching. A 28kDa band was identified as PEB3, a previously characterized immunogenic cell surface protein. Bands of 32 and 34kDa were both identified as a putative periplasmic protein encoded by the C. jejuni NCTC 11168 coding sequence Cj1670c. We have named this putative glycoprotein CgpA. We constructed insertional knockout mutants of both the peb3 and cgpA genes, and surface protein extracts from mutant and wild-type strains were analysed by one- and two-dimensional polyacrylamide gel electrophoresis (PAGE). In this way, we were able to identify the PEB3 protein as a 28 kDa SBA-reactive and immunoreactive glycoprotein. The cgpA gene encoded SBA-reactive and immunoreactive proteins of 32 and 34 kDa. By using specific exoglycosidases, we demonstrated that the SBA binding property of acid-glycine extractable C. jejuni glycoproteins, including PEB3 and CgpA, is a result of the presence of alpha-linked N-acetylgalactosamine residues. These data confirm the existence, and extend the boundaries, of the previously identified protein glycosylation locus of C. jejuni. Furthermore, we have identified two such glycoproteins, the first non-flagellin campylobacter glycoproteins to be identified, and demonstrated that their glycan components contain alpha-linked N-acetylgalactosamine residues.

Ssf1p prevents premature processing of an early pre-60S ribosomal particle.

Ssf1p and Ssf2p are two nearly identical and functionally redundant nucleolar proteins. In the absence of Ssf1p and Ssf2p, the 27SA(2) pre-rRNA was prematurely cleaved, inhibiting synthesis of the 27SB and 7S pre-rRNAs and the 5.8S and 25S rRNA components of the large ribosomal subunit. On sucrose gradients, Ssf1p sedimented with pre-60S ribosomal particles. The 27SA(2), 27SA(3), and 27SB pre-rRNAs were copurified with tagged Ssf1p, as were 23 large subunit ribosomal proteins and 21 other proteins implicated in ribosome biogenesis. These included four Brix family proteins, Ssf1p, Rpf1p, Rpf2p, and Brx1p, indicating that the entire family functions in ribosome synthesis. This complex is distinct from recently reported pre-60S complexes in RNA and protein composition. We describe a multistep pathway of 60S preribosome maturation.