Comparison of glycoprotein hormone alpha-subunits of laboratory animals

The common alpha-subunit of glycoprotein hormones (CGalpha) is a core protein shared by follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyroid-stimulating hormone (TSH). In order to obtain a molecular basis for an efficient superovulation technique applicable to a wide range of animal species and to discuss the phylogenetic aspect based on molecules related to the reproductive system, we determined cDNA sequences of CGalpha in seven laboratory animals: the guinea pig, Mongolian gerbil, golden hamster, mastomys, Japanese field vole, the JF1 strain of Mus musculus molossinus, and rabbit. Comparison of the inferred CGalpha amino acid sequences of these animals and other mammals (human, mouse, rat, cow, pig, and sheep) showed that the signal peptides and the first ten residues at the N-terminus of the apoprotein were variable, while the rest of the apoproteins were highly conserved. In particular, all rodents had a leucine residue at the apoprotein N-terminus, except the guinea pig, which had a phenylalanine residue, as in the cow, pig, sheep, and rabbit. Phylogenetic trees constructed from amino acid sequences suggest a closer relationship between the guinea pig and artiodactyls than to rodents, confirming the taxonomic peculiarity of the guinea pig.     

A New Mouse Allele of Glutamate Receptor Delta 2 with Cerebellar Atrophy and Progressive Ataxia

Spinocerebellar degenerations (SCDs) are a large class of sporadic or hereditary neurodegenerative disorders characterized by progressive motion defects and degenerative changes in the cerebellum and other parts of the CNS. Here we report the identification and establishment from a C57BL/6J mouse colony of a novel mouse line developing spontaneous progressive ataxia, which we refer to as ts3. Frequency of the phenotypic expression was consistent with an autosomal recessive Mendelian trait of inheritance, suggesting that a single gene mutation is responsible for the ataxic phenotype of this line. The onset of ataxia was observed at about three weeks of age, which slowly progressed until the hind limbs became entirely paralyzed in many cases. Micro-MRI study revealed significant cerebellar atrophy in all the ataxic mice, although individual variations were observed. Detailed histological analyses demonstrated significant atrophy of the anterior folia with reduced granule cells (GC) and abnormal morphology of cerebellar Purkinje cells (PC). Study by ultra-high voltage electron microscopy (UHVEM) further indicated aberrant morphology of PC dendrites and their spines, suggesting both morphological and functional abnormalities of the PC in the mutants. Immunohistochemical studies also revealed defects in parallel fiber (PF)–PC synapse formation and abnormal distal extension of climbing fibers (CF). Based on the phenotypic similarities of the ts3 mutant with other known ataxic mutants, we performed immunohistological analyses and found that expression levels of two genes and their products, glutamate receptor delta2 (grid2) and its ligand, cerebellin1 (Cbln1), are significantly reduced or undetectable. Finally, we sequenced the candidate genes and detected a large deletion in the coding region of the grid2 gene. Our present study suggests that ts3 is a new allele of the grid2 gene, which causes similar but different phenotypes as compared to other grid2 mutants.     

Polyethylenimine-cationized β-catenin protein transduction activates the Wnt canonical signaling pathway more effectively than cationic lipid-based transduction

The Wnt canonical signaling pathway is essential for the early development of eukaryotic organisms and plays a key role in cell proliferation, differentiation, and oncogenesis. Moreover, the Wnt canonical signaling pathway contributes to the self-renewal of mouse hematopoietic stem cells (HSCs). Here, we demonstrate artificial activation of the Wnt canonical signaling pathway by β-catenin protein transduction. Constitutively active β-catenin protein was introduced into human embryonic kidney HEK-293 cells using a polyethylenimine (PEI) cationization method, or with the BioPORTER protein transduction reagent. We have previously shown that modification with PEI effectively causes proteins to be internalized by living mammalian cells. PEI-cationized, constitutively active β-catenin protein was added to HEK-293 cells, and induction of several Wnt/β-catenin target genes was detected by real-time PCR. However, using BioPORTER to introduce active β-catenin did not activate the Wnt canonical signaling pathway. Introduction of eGFPNuc (enhanced green fluorescent protein variant containing a nuclear localization signal) into HEK-293 cells using the BioPORTER reagent caused significant cell death, as determined by propidium iodide staining. In contrast, the PEI-modified eGFPNuc did not impair survival of HEK-293 cells. These results indicate that the Wnt canonical signaling pathway could be successfully activated by transduction of PEI-cationized active β-catenin, and the PEI-cationization method is an effective and safe technology for protein transduction into mammalian cells.     

A torque component in the kinesin-1 power stroke

Kinesin-1 is a twin-headed molecular motor that moves along microtubules in 8-nm steps, using a walking action in which the two heads interact alternately with the microtubule. Constructs with only one head can also produce impulses of force and motion, indicating that the walking action is an amplification strategy that leverages an underlying force-generating event. Recent work suggests that directional force is produced either by directionally biased selection of microtubule binding sites or by a conformational change subsequent to the binding event. We report here that surface-attached rat kinesin-1 monomers drive counterclockwise rotation of sliding microtubules around their axes, and that by manipulating the assay geometry, we could reduce or block the torsional motion with negligible effects on the axial motion. We can account for this behavior on the simple assumption that kinesin heads tend to bind to the closest available tubulin heterodimer in the lattice, but only in the case where an additional biasing process is present that shifts the start position for diffusion-to-capture toward the microtubule plus end by approximately 1 nm.     

An indispensable role for STAT1 in IL-27-induced T-bet expression but not proliferation of naive CD4+ T cells

IL-27 is a novel IL-12 family member that plays a role in the early regulation of Th1 initiation, induces proliferation of naive CD4+ T cells, and synergizes with IL-12 in IFN-gamma production. It has been recently reported that IL-27 induces T-bet and IL-12Rbeta2 expression through JAK1/STAT1 activation. In the present study, we further investigated the JAK/STAT signaling molecules activated by IL-27 and also the role of STAT1 in IL-27-mediated responses using STAT1-deficient mice. In addition to JAK1 and STAT1, IL-27-activated JAK2, tyrosine kinase-2, and STAT2, -3, and -5 in naive CD4+ T cells. The activation of STAT2 and STAT5, but not of STAT3, was greatly diminished in STAT1-deficient naive CD4+ T cells. Comparable proliferative response to IL-27 was observed between STAT1-deficient and wild-type naive CD4+ T cells. In contrast, IL-27 hardly induced T-bet and subsequent IL-12Rbeta2 expression, and synergistic IFN-gamma production by IL-27 and IL-12 was impaired in STAT1-deficient naive CD4+ T cells. Moreover, IL-27 augmented the expression of MHC class I on naive CD4+ T cells in a STAT1-dependent manner. These results suggest that IL-27 activates JAK1 and -2, tyrosine kinase-2, STAT1, -2, -3, and -5 in naive CD4+ T cells and that STAT1 plays an indispensable role in IL-27-induced T-bet and subsequent IL-12Rbeta2 expression and MHC class I expression as well but not proliferation, while STAT3 presumably plays an important role in IL-27-induced proliferation.     

Induction of IgG2a class switching in B cells by IL-27

IL-27 is a novel IL-12 family member that plays a role in the early regulation of Th1 initiation. However, its role in B cells remains unexplored. We here show a role for IL-27 in the induction of T-bet expression and regulation of Ig class switching in B cells. Expression of WSX-1, one subunit of IL-27R, was detected at the mRNA level in primary mouse spleen B cells, and stimulation of these B cells by IL-27 rapidly activated STAT1. IL-27 then induced T-bet expression and IgG2a, but not IgG1, class switching in B cells activated with anti-CD40 or LPS. In contrast, IL-27 inhibited IgG1 class switching induced by IL-4 in activated B cells. Similar induction of STAT1 activation, T-bet expression and IgG2a class switching was observed in IFN-gamma-deficient B cells, but not in STAT1-deficient ones. The induction of IgG2a class switching was abolished in T-bet-deficient B cells activated with LPS. These results suggest that primary spleen B cells express functional IL-27R and that the stimulation of these B cells by IL-27 induces T-bet expression and IgG2a, but not IgG1, class switching in a STAT1-dependent but IFN-gamma-independent manner. The IL-27-induced IgG2a class switching is highly dependent on T-bet in response to T-independent stimuli such as LPS. Thus, IL-27 may be a novel attractive candidate as a therapeutic agent against diseases such as allergic disorders by not only regulating Th1 differentiation but also directly acting on B cells and inducing IgG2a class switching.     

GPR40 gene expression in human pancreas and insulinoma

To assess gene expression of a membrane-bound G-protein-coupled fatty acid receptor, GPR40, in the human pancreas and islet cell tumors obtained at surgery were analyzed. The mRNA level of the GPR40 gene in isolated pancreatic islets was approximately 20-fold higher than that in the pancreas, and the level was comparable to or rather higher than that of the sulfonylurea receptor 1 gene, which is known to be expressed abundantly in human pancreatic beta cells. A large amount of GPR40 mRNA was detected in tissue extracts from two cases of insulinoma, whereas the expression was undetectable in glucagonoma or gastrinoma. The present study demonstrates that GPR40 mRNA is expressed predominantly in pancreatic islets in humans and that GPR40 mRNA is expressed solely in human insulinoma among islet cell tumors. These results indicate that GPR40 is probably expressed in pancreatic beta cells in the human pancreas.     

Stabilization due to dimer formation of phosphoribosyl anthranilate isomerase from Thermus thermophilus HB8: X-ray Analysis and DSC experiments

The crystal structure of phosphoribosyl anthranilate isomerase (PRAI) from Thermus thermophilus HB8 (TtPRAI) was solved at 2.0 A resolution. The overall structure of TtPRAI with a dimeric structure was quite similar to that of PRAI from Thermotoga maritima (TmPRAI). In order to elucidate the stabilization mechanism of TtPRAI, its physicochemical properties were examined using DSC, CD, and analytical centrifugation at various pHs in relation to the association-dissociation of the subunits. Based on the experimental results for TtPRAI and the structural information on TtPRAI and TmPRAI, we found that: (i) the denaturation of TtPRAI at acidic pH is correlated with the dissociation of its dimeric form; (ii) the hydrophobic interaction of TtPRAI in the monomer structure is slightly greater than that of TmPRAI, but dimer interface of the TmPRAI is remarkably greater; (iii) the contributions of hydrogen bonds and ion bonds to the stability are similar to each other; and (iv) destabilization due to the presence of cavities in TtPRAI is greater than that of TmPRAI in both the monomer and dimer structures.     

Prominent immunogenicity of monosialosyl galactosylgloboside, carrying a stage-specific embryonic antigen-4 (SSEA-4) epitope in the ACHN human renal tubular cell line—a simple method for producing monoclonal antibodies against detergent-insoluble microdomains/raft

The binding of Shiga toxin (Stx) to Gb3Cer in detergent-insoluble microdomains (DIM)/raft of the ACHN human renal tubular cell line causes the temporal activation of the Src-family kinase Yes [1]. As a strategy for examining signaling mechanisms in DIM/raft, monoclonal antibodies (MAbs) are reliable tools for characterizing the constituent molecules in these microdomains. Thus, we employed DIM/raft suspensions of ACHN cells as an immunogen to develop MAbs. Simply subcutaneous injections of ACHN DIM/raft could elevate the serum titer after several boosts. The first screening was performed using dot-blot immunostaining with culture supernatants on a polyvinylidene difluoride (PVDF) membrane, on which DIM/raft or their chloroform/methanol (C/M) (2:1, v/v) extracts were dot-blotted. The next screening was performed by flowcytometric analysis of ACHN cells treated with or without a permeabilizing reagent. Many of the clones (21/31 clones=68%) thus obtained were also found to recognize to lipid fractions of the DIM/raft. Strikingly, all of the 21 clones that reacted to the lipid fraction were found to recognize monosialosyl galactosylgloboside (MSGG) or GL7, which carries the SSEA-4 epitope. Using DIM/raft as immunogens may enable us to easily obtain MAbs for glycolipids.