Western blot analysis of epidermal growth factor using gelatin-coated polyvinylidene difluoride membranes

A new approach to detect small peptides clearly and sensitively by Western blotting using a vacuum-assisted detection method

Western blotting is a widely used technique for the detection and quantification of proteins and peptides. However, it is challenging to detect small peptides efficiently by the conventional Western blotting method with shaking, in part because the peptides readily detach from the blotted membrane. Although some modified Western blotting protocols have been developed to overcome this problem, it remains difficult to prevent peptide detachment from the membrane. In this study, we show that the previously developed vacuum-assisted detection method greatly improves the detection of small peptides without additional protocol modification. The vacuum-assisted method was developed to shorten the time required for all immunodetection steps, and all the Western blotting solutions penetrated the membrane quickly and efficiently by this method. By using this vacuum method, we succeeded in detecting small peptides that were completely undetectable by the conventional Western blotting method. We also confirmed that peptide detachment was induced even by gentle shaking in the case of the conventional method, and the detachment was accelerated when detergent was present in the buffer. Unlike in the conventional method, there is no need to shake the membrane in solution in the vacuum method. Therefore, it is thought that the small peptides could be detected sensitively only by the vacuum method.

Functional and structural bases of a cysteine-less mutant as a long-lasting substitute for galectin-1

Galectin-1 (Gal-1), a member of the beta-galactoside-binding animal lectin family, has a wide range of biological activities, which makes it an attractive target for medical applications. Unlike other galectins, Gal-1 is susceptible to oxidation at cysteine residues, which is troublesome for in vitro/vivo studies. To overcome this problem, we prepared a cysteine-less mutant of Gal-1 (CSGal-1) by substituting all cysteine residues with serine residues. In the case of wild-type Gal-1, the formation of covalent dimers/oligomers was evident after 10 days of storage in the absence of a reducing agent with a concomitant decrease in hemagglutination activity, while CSGal-1 did not form multimers and retained full hemagglutination activity after 400 days of storage. Frontal affinity chromatography showed that the sugar-binding specificity and affinity of Gal-1 for model glycans were barely affected by the mutagenesis. Gal-1 is known to induce cell signaling leading to an increase in the intracytoplasmic calcium concentration and to cell death. CSGal-1 is also capable of inducing calcium flux and growth inhibition in Jurkat cells, which are comparable to or more potent than those induced by Gal-1. The X-ray structure of the CSGal-1/lactose complex has been determined. The structure of CSGal-1 is almost identical to that of wild-type human Gal-1, showing that the amino acid substitutions do not affect the overall structure or carbohydrate-binding site structure of the protein. These results indicate that CSGal-1 can serve as a stable substitute for Gal-1.

Galectin-8 modulates neutrophil function via interaction with integrin alphaM

The members of the galectin family are associated with diverse cellular events, including immune response. We investigated the effects of galectin-8 on neutrophil function. Human galectin-8 induced firm and reversible adhesion of peripheral blood neutrophils but not eosinophils to a plastic surface in a lactose-sensitive manner. Other human galectins, galectins-1, -3, and -9, showed low or negligible effects on neutrophil adhesion. Confocal microscopy revealed actin bundle formation in the presence of galectin-8. Cytochalasins inhibited both actin assembly and cell adhesion induced by galectin-8. Affinity purification of galectin-interacting proteins from solubilized neutrophil membrane revealed that N-terminal carbohydrate recognition domain (CRD) of galectin-8 bound promatrix metalloproteinase-9 (proMMP-9), and C-terminal CRD bound integrin alphaM/CD11b and proMMP-9. A mutant galectin-8 lacking the carbohydrate-binding activity of N-terminal CRD (galectin-8R69H) retained adhesion-inducing activity, but inactivation of C-terminal CRD (galectin-8R233H) abolished the activity. MMP-3-mediated processing of proMMP-9 was accelerated by galectin-8, and this effect was inhibited by lactose. Galectins-1 and -3 did not affect the processing. Superoxide production, an essential event in bactericidal function of neutrophils, was stimulated by galectin-8 to an extent comparable to that induced by fMLP. Galectin-8R69H but not galectin-8R233H could stimulate superoxide production. Taken together, these results suggest that galectin-8 is a novel factor that modulates the neutrophil function related to transendothelial migration and microbial killing.

Collagen-binding growth factors: production and characterization of functional fusion proteins having a collagen-binding domain

The autocrine/paracrine peptide signaling molecules such as growth factors have many promising biologic activities for clinical applications. However, one cannot expect specific therapeutic effects of the factors administered by ordinary drug delivery systems as they have limited target specificity and short half-lives in vivo. To overcome the difficulties in using growth factors as therapeutic agents, we have produced fusion proteins consisting of growth factor moieties and a collagen-binding domain (CBD) derived from Clostridium histolyticum collagenase. The fusion proteins carrying the epidermal growth factor (EGF) or basic fibroblast growth factor (bFGF) at the N terminal of CBD (CBEGF/CBFGF) tightly bound to insoluble collagen and stimulated the growth of BALB/c 3T3 fibroblasts as much as the unfused counterparts. CBEGF, when injected subcutaneously into nude mice, remained at the sites of injection for up to 10 days, whereas EGF was not detectable 24 h after injection. Although CBEGF did not exert a growth-promoting effect in vivo, CBFGF, but not bFGF, strongly stimulated the DNA synthesis in stromal cells at 5 days and 7 days after injection. These results indicate that CBD may be used as an anchoring unit to produce fusion proteins nondiffusible and long-lasting in vivo.

Epidermal growth factor in the rat prostate: production, tissue content and molecular forms in the different prostatic lobes

BACKGROUND

Epidermal growth factor (EGF) induces proliferation in prostate epithelial and stromal cells in primary culture. This investigation was set up to characterize the time and spatial expression of EGF in the rat prostate.

METHODS

The expression of EGF was characterized in the distinct lobes of the rat prostate by means of ELISA, gel filtration, immunohistochemistry, and in situ hybridization.

RESULTS

Local synthesis of EGF by the luminal epithelium was demonstrated by in situ hybridization in the dorsal lobe only. This lobe contained the major part of the prostatic EGF with a sixfold higher concentration than measured in the lateral lobe, and 300-fold higher than in the ventral lobe. Rat prostatic EGF was found to consist of at least two high-molecular-weight forms, as well as a 6-kDa form. The high-molecular-weight forms made up approximately 40% of the EGF measured in the dorsal rat prostate. At 8-12 weeks of age, the concentration of EGF in the dorsal lobe was doubled, with no further increase up to 16 weeks.

CONCLUSIONS

We report a 300-fold difference in the lobar content of EGF in the rat prostate, and a doubling of the concentration at 8-12 weeks of age.

Isolation and characterization of invasive and noninvasive variants of a rat bladder tumor cell line

We isolated, in vitro, spontaneous variants of the rat bladder tumor NBT-II cell line with a distinctive morphology. Of five sublines obtained, three (NBT-L1, L2a and L2b) exhibited an elongated shape and moderate to high invasive activity in vitro. The other two sublines (NBT-T1 and T2) formed tight colonies and exhibited very low or negligible invasive activity. The contents of mRNAs coding for E-cadherin and cadherin-associated molecules (alpha-catenin and beta-catenin) were not correlated with the invasive activity of the cells. However, the expression level of the E-cadherin protein, but not those of catenins, was lower in invasive cells (NBT-L1, L2a and L2b) than in noninvasive cells (NBT-T1 and T2). Analysis of mRNAs coding for several growth factors and their receptors showed that the transforming growth factor alpha mRNA content in invasive cells was higher than that in noninvasive cells, and that the content of epidermal growth factor receptor mRNA was low in NBT-T2. Although NBT-II is known to acquire a fibroblastic appearance and cell motility in response to several growth factors, the conditioned media of the invasive sublines hardly affected the morphology or motility of noninvasive cells. These results indicate that the decreased E-cadherin expression is closely associated with the transition from the noninvasive to the invasive phenotype of the bladder tumor cells, and that a post-transcriptional process is important in the control of E-cadherin expression in the cells. These sublines may be useful as models for studies on the progression of bladder tumors.