An integrated workflow for extraction and solubilization of intermediate filaments from colorectal biopsies for proteomic analysis.

We report a technique for isolation and solubilization of intermediate filament (IF) proteins from colonic biopsies compatible with both gel electrophoresis and liquid chromatography "shotgun" proteomics using mass spectrometry (MS). This is important because changes in the IF proteome, particularly in keratin expression and modification, are noted in colonic mucosa of patients with colorectal cancer. Though keratins have traditionally been dissolved in high concentration of urea, the latter solvent precludes efficient proteolytic digestion by trypsin prior to gel-free LC-MS/MS approaches. The extraction of cytoskeletal proteins was initially evaluated using MCF-7 cancer cell lines using a published, differential detergent solubilization protocol. IF proteins were extracted from colonic biopsies using a combination of homogenization and sonication. Since comparable efficiency of solubilization was noted on the extracted IF from cell lines between urea and guanidine hydrochloride (GuHCl) in triethylammonium bicarbonate buffer, isolated proteins from endoscopic biopsies were solubilized in GuHCl. Using immunoblotting techniques, we successfully demonstrated isolation of keratins and preservation of posttranslational modifications (phosphorylation, acetylation). Dissolved proteins were tryptically digested and peptides analyzed by MS, showing the functionality of the workflow in shotgun proteomic applications, specifically compatibility of the workflow for isobaric tagging relative and absolute quantification based quantitation approaches.

Preclinical evaluation of an inhibitor of cytosolic phospholipase A2α for the treatment of asthma.

Asthma is a chronic inflammatory lung disease with considerable unmet medical needs for new and effective therapies. Cytosolic phospholipase A(2)α (cPLA(2)α) is the rate-limiting enzyme that is ultimately responsible for the production of eicosanoids implicated in the pathogenesis of asthma. We investigated a novel cPLA(2)α inhibitor, PF-5212372, to establish the potential of this drug as a treatment for asthma. PF-5212372 was a potent inhibitor of cPLA(2)α (7 nM) and was able to inhibit prostaglandin (PG)D(2) and cysteinyl leukotriene release from anti-IgE-stimulated human lung mast cells (0.29 and 0.45 nM, respectively). In a mixed human lung cell population, PF-5212372 was able to inhibit ionomycin-stimulated release of leukotriene B(4), thromboxane A(2), and PGD(2) (2.6, 2.6, and 4.0 nM, respectively) but was significantly less effective against PGE(2) release (>301 nM; p < 0.05). In an in vitro cell retention assay, PF-5212372 retained its potency up to 24 h after being washed off. In a sheep model of allergic inflammation, inhalation of PF-5212372 significantly inhibited late-phase bronchoconstriction (78% inhibition; p < 0.001) and airway hyper-responsiveness (94% inhibition; p < 0.001), and isolated sheep lung mast cell assays confirmed species translation via effective inhibition of PGD(2) release (0.78 nM). Finally, PF-5212372 was assessed for its ability to inhibit the contraction of human bronchi induced by AMP. PF5212372 significantly inhibited AMP-induced contraction of human bronchi (81% inhibition; p < 0.001); this finding, together with the ability of this drug to be effective in a wide range of preclinical asthma models, suggests that inhibition of cPLA(2)α with PF-5212372 may represent a new therapeutic option for the treatment of asthma.

SPLUNC1 (PLUNC) is expressed in glandular tissues of the respiratory tract and in lung tumours with a glandular phenotype.

Short PLUNC1 (SPLUNC1) is the founding member of a novel family of proteins (PLUNC) expressed in the upper respiratory tract that may function in host defence. It is one of the most highly expressed genes in the upper airways and the protein has been detected in sputum and nasal secretions. This study describes, for the first time, the precise cellular localization of SPLUNC1 in human tissues from the respiratory tract. Although SPLUNC1 is found in some epithelial cells of the upper airways and coats the surface epithelial cell lining of the major airways, the most significant site of protein localization is in mucous cells and ducts of submucosal glands. Intense staining is also seen in minor glands of the nose, sinuses, posterior tongue and tonsil, suggesting that the protein is secreted into mucoid secretions of these tissues, where it probably functions in host defence. No staining was seen in peripheral lung tissue. As SPLUNC1 has been suggested to be a novel lung cancer marker, a limited panel of lung cancers was also studied. The findings suggest that SPLUNC1 is commonly expressed in adenocarcinomas, muco-epidermoid carcinoma, and bronchio-alveloar carcinoma, and is absent from small-cell carcinoma and squamous cell carcinoma. This expression pattern is consistent with the presumed phenotypic origin of these tumours and suggests that SPLUNC1 may be a useful marker for lung cancer.

Phylogenetic and evolutionary analysis of the PLUNC gene family.

The PLUNC family of human proteins are candidate host defense proteins expressed in the upper airways. The family subdivides into short (SPLUNC) and long (LPLUNC) proteins, which contain domains predicted to be structurally similar to one or both of the domains of bactericidal/permeability-increasing protein (BPI), respectively. In this article we use analysis of the human, mouse, and rat genomes and other sequence data to examine the relationships between the PLUNC family proteins from humans and other species, and between these proteins and members of the BPI family. We show that PLUNC family clusters exist in the mouse and rat, with the most significant diversification in the locus occurring for the short PLUNC family proteins. Clear orthologous relationships are established for the majority of the proteins, and ambiguities are identified. Completion of the prediction of the LPLUNC4 proteins reveals that these proteins contain approximately a 150-residue insertion encoded by an additional exon. This insertion, which is predicted to be largely unstructured, replaces the structure homologous to the 40s hairpin of BPI. We show that the exon encoding this region is anomalously variable in size across the LPLUNC proteins, suggesting that this region is key to functional specificity. We further show that the mouse and human PLUNC family orthologs are evolving rapidly, which supports the hypothesis that these proteins are involved in host defense. Intriguingly, this rapid evolution between the human and mouse sequences is replaced by intense purifying selection in a large portion of the N-terminal domain of LPLUNC4. Our data provide a basis for future functional studies of this novel protein family.