Evolution of Pinnipedia lactation strategies: a potential role for α-lactalbumin?

Despite the considerable variation in milk composition found among mammals, a constituent common across all groups is lactose, the main sugar and osmole in most eutherians milk. Exceptions to this are the families Otariidae (fur seals and sea lions) and Odobenidae (walruses), where lactose has not been detected. We investigated the molecular basis for this by cloning alpha-lactalbumin, the modifier protein of the lactose synthase complex. A mutation was observed which, in addition to preventing lactose production, may enable otariids to maintain lactation despite the extremely long inter-suckling intervals during the mother's time at sea foraging (more than 23 days in some species).     

Ultrastructural localization of integrin subunits beta4 and alpha3 within the migrating epithelial tongue of in vivo human wounds

Subsequent to wounding, keratinocytes must quickly restore barrier function. In vitro wound models have served to elucidate mechanisms of epithelial closure and key roles for integrins alpha6beta4 and alpha3beta1. To extrapolate in vitro data to in vivo human tissues, we used ultrathin cryomicrotomy to simultaneously observe tissue ultrastructure and immunogold localization in unwounded skin and acute human cutaneous wounds. Localization of the beta4 integrin subunit in unwounded skin shows dominant hemidesmosomal association and minor basal keratinocyte lateral filopodic cell-cell expression. After wounding, beta4 dominantly localized to cytokeratin-rich regions (trailing edge hemidesmosomes) and minor association with lamellipodia (leading edge). beta4 colocalizes with alpha3 within filopodia juxtaposed to wound matrix, and increased concentrations of beta4 were found in cytoplasmic vesicles within basal keratinocytes of the migrating tongue. alpha3 integrin subunit dominantly localized to filopodia within basal keratinocyte lateral cell-cell interfaces in unwounded skin and both cell-cell and cell-matrix filopodic interactions in wounded skin. This study indicates that beta4 interacts with the extracellular environment through both stable and transient interactions and may be managed through a different endosomal trafficking pathway than alpha3. alpha3 integrin, despite its ability to respond to alternate ligands after wounding, does so through a single structure, the filopodia.     

The integrin alpha9beta1 mediates adhesion to activated endothelial cells and transendothelial neutrophil migration through interaction with vascular cell adhesion molecule-1

The integrin alpha9beta1 has been shown to be widely expressed on smooth muscle and epithelial cells, and to mediate adhesion to the extracellular matrix proteins osteopontin and tenascin-C. We have found that the peptide sequence this integrin recognizes in tenascin-C is highly homologous to the sequence recognized by the closely related integrin alpha4beta1, in the inducible endothelial ligand, vascular cell adhesion mole-cule-1 (VCAM-1). We therefore sought to determine whether alpha9beta1 also recognizes VCAM-1, and whether any such interaction would be biologically significant. In this report, we demonstrate that alpha9beta1 mediates stable cell adhesion to recombinant VCAM-1 and to VCAM-1 induced on human umbilical vein endothelial cells by tumor necrosis factor-alpha. Furthermore, we show that alpha9beta1 is highly and selectively expressed on neutrophils and is critical for neutrophil migration on VCAM-1 and tenascin-C. Finally, alpha9beta1 and alpha4 integrins contribute to neutrophil chemotaxis across activated endothelial monolayers. These observations suggest a possible role for alpha9beta1/VCAM-1 interactions in extravasation of neutrophils at sites of acute inflammation.     

EstB from Burkholderia gladioli: a novel esterase with a beta-lactamase fold reveals steric factors to discriminate between esterolytic and beta-lactam cleaving activity

Esterases form a diverse class of enzymes of largely unknown physiological role. Because many drugs and pesticides carry ester functions, the hydrolysis of such compounds forms at least one potential biological function. Carboxylesterases catalyze the hydrolysis of short chain aliphatic and aromatic carboxylic ester compounds. Esterases, D-alanyl-D-alanine-peptidases (DD-peptidases) and beta-lactamases can be grouped into two distinct classes of hydrolases with different folds and topologically unrelated catalytic residues, the one class comprising of esterases, the other one of beta-lactamases and DD-peptidases. The chemical reactivities of esters and beta-lactams towards hydrolysis are quite similar, which raises the question of which factors prevent esterases from displaying beta-lactamase activity and vice versa. Here we describe the crystal structure of EstB, an esterase isolated from Burkholderia gladioli. It shows the protein to belong to a novel class of esterases with homology to Penicillin binding proteins, notably DD-peptidase and class C beta-lactamases. Site-directed mutagenesis and the crystal structure of the complex with diisopropyl-fluorophosphate suggest Ser75 within the "beta-lactamase" Ser-x-x-Lys motif to act as catalytic nucleophile. Despite its structural homology to beta-lactamases, EstB shows no beta-lactamase activity. Although the nature and arrangement of active-site residues is very similar between EstB and homologous beta-lactamases, there are considerable differences in the shape of the active site tunnel. Modeling studies suggest steric factors to account for the enzyme's selectivity for ester hydrolysis versus beta-lactam cleavage.     

The brown seaweed Sargassum hemiphyllum exhibits α-amylase and α-glucosidase inhibitory activity and enhances insulin release in vitro

Diabetes is one of the most prevalent chronic diseases globally. In this study, major polyphenols (17.35 ± 0.93–36.66 ± 2.01 mg/g) and minor fucoxanthin (non detected 15.12 ± 0.09 mg/g) were isolated from water, ethanol, and acetone extracts (WES, EES, and AES, respectively) of Sargassum hemiphyllum. Inhibition of α-amylase, α-glucosidase, sucrose, and maltase activities and stimulation of insulin secretion was greater with AES than with WES or EES and correlated with polyphenol and fucoxanthin concentrations in extracts. Moreover, 250 μg/ml EES and AES significantly increased insulin secretion in the presence of 25 mg/ml glibenclamide to higher levels than those obtained with 50 mg/ml glibenclamide. None of the extracts exhibited cytotoxicity, exacerbated the side effects of glibenclamide, or inhibited glibenclamide-induced insulin secretion. These results suggested that the S. hemiphyllum extracts WES, EES, and AES could be used as pharmaceuticals and functional foods to reduce dosages of synthetic diabetes drugs.