Primary structure of Electrophorus electricus sodium channel deduced from cDNA sequence

Cloning and sequence analysis of cDNA for the Electrophorus electricus electroplax sodium channel indicate that this protein, consisting of 1,820 amino acid residues, exhibits four repeated homology units, which are presumably oriented in a pseudosymmetric fashion across the membrane. Each homology unit contains a unique segment with clustered positively charged residues, which may be involved in the gating structure, possibly in conjunction with negatively charged residues clustered elsewhere.

FcR gamma chain deletion results in pleiotrophic effector cell defects

The gamma subunit of immunoglobulin Fc receptors is an essential component of the high-affinity receptor for IgG (Fc gamma RIII) and is associated with the high-affinity receptor for IgG (Fc gamma RI) and the T cell receptor-CD3 complex. It is required for both receptor assembly and signal transduction. Targeted disruption of this subunit results in immunocompromised mice. Activated macrophages from gamma chain-deficient mice unexpectedly lack the ability to phagocytose antibody-coated particles, despite normal binding. Defects in NK cell-mediated antibody-dependent cytotoxicity and mast cell-mediated allergic responses are evident in these animals, establishing the indispensable role of FcRs in these responses. However, loss of gamma chain does not appear to perturb T cell development, since both thymic and peripheral T cell populations appear normal. These mice thus represent an important tool for evaluating the role of these receptors in humoral and cellular immune responses.

Molecular distinction between fetal and adult forms of muscle acetylcholine receptor

Distinct classes of acetylcholine receptor channels are formed when Xenopus oocytes are injected with combinations of the bovine alpha-, beta-, gamma- and delta- or the alpha-, beta-, gamma- and epsilon-subunit-specific messenger RNAs. The conductance and gating properties of the two classes of channels, in conjunction with the developmental changes in the muscular contents of the mRNAs, suggest that replacement of the gamma-subunit by the epsilon-subunit is responsible for the functional alteration of the receptor during muscle development.

Augmented humoral and anaphylactic responses in Fc gamma RII-deficient mice

Despite its widespread distribution on both lymphoid and myeloid cells, the biological role of the low-affinity immunoglobulin-G receptor, Fc gamma RII, is not fully understood. Defects in this receptor or its signalling pathway in B cells result in perturbations in immune-complex-mediated feedback inhibition of antibody production. We now report that Fc gamma RII-deficient animals display elevated immunoglobulin levels in response to both thymus-dependent and thymus-independent antigens. Additionally, the effector arm of the allergic response is perturbed in these mice. Mast cells from Fc gamma RII-/- are highly sensitive to IgG-triggered degranulation, in contrast to their wild-type counterparts. Fc gamma RII-deficient mice demonstrate an enhanced passive cutaneous analphylaxis reaction, the result of a decreased threshold for mast-cell activation by Fc gamma RIII cross-linking. These results demonstrate that Fc gamma RII acts as a general negative regulator of immune-complex-triggered activation in vivo for both the afferent and efferent limbs of the immune response. Exploiting this property offers new therapeutic opportunities for the treatment of allergic and autoimmune disorders.

Modulation of immune complex-induced inflammation in vivo by the coordinate expression of activation and inhibitory Fc receptors

Autoantibodies and immune complexes are major pathogenic factors in autoimmune injury, responsible for initiation of the inflammatory cascade and its resulting tissue damage. This activation results from the interaction of immunoglobulin (Ig)G Fc receptors containing an activation motif (ITAM) with immune complexes (ICs) and cytotoxic autoantibodies which initiates and propagates an inflammatory response. In vitro, this pathway can be interrupted by coligation to FcgammaRIIB, an IgG Fc receptor containing an inhibitory motif (ITIM). In this report, we describe the in vivo consequences of FcgammaRII deficiency in the inflammatory response using a mouse model of IC alveolitis. At subthreshold concentrations of ICs that fail to elicit inflammatory responses in wild-type mice, FcgammaRII-deficient mice developed robust inflammatory responses characterized by increased hemorrhage, edema, and neutrophil infiltration. Bronchoalveolar fluids from FcgammaRII-/- stimulated mice contain higher levels of tumor necrosis factor and chemotactic activity, suggesting that FcgammaRII deficiency lowers the threshold of IC stimulation of resident cells such as the alveolar macrophage. In contrast, complement- and complement receptor-deficient mice develop normal inflammatory responses to suprathreshold levels of ICs, while FcRgamma-/- mice are completely protected from inflammatory injury. An inhibitory role for FcgammaRII on macrophages is demonstrated by analysis of FcgammaRII-/- macrophages which show greater phagocytic and calcium flux responses upon FcgammaRIII engagement. These data reveal contrasting roles for the cellular receptors for IgG on inflammatory cells, providing a regulatory mechanism for setting thresholds for IC sensitivity based on the ratio of ITIM to ITAM FcgammaR expression. Exploiting the FcgammaRII inhibitory pathway could thus provide a new therapeutic approach for modulating antibody-triggered inflammation.

Deletion of fcgamma receptor IIB renders H-2(b) mice susceptible to collagen-induced arthritis

Autoimmune diseases, like rheumatoid arthritis, result from a dysregulation of the immune response culminating in hyperactivation of effector cells leading to immune-mediated injury. To maintain an appropriate immune response and prevent the emergence of autoimmune disease, activation signals must be regulated by inhibitory pathways. Biochemical and genetic studies indicate that the type IIB low-affinity receptor for immunoglobulin (Ig)G (FcgammaRIIB) inhibits cellular activation triggered through antibody or immune complexes and may be an important component in preventing the emergence of autoimmunity. To investigate the role of FcgammaRIIB in the development of type II collagen (CII)-induced arthritis (CIA), a model for rheumatoid arthritis in humans, we have examined its contribution in determining the susceptibility to CIA in the nonpermissive H-2(b) haplotype. H-2(b) mice immunized with bovine CII do not develop appreciable disease. In contrast, immunization of the FcgammaRIIB-deficient, H-2(b) mice with bovine CII induced CIA at an incidence of 42.2%. The maximal arthritis index of the FcgammaRIIB-deficient mice developing CIA (6.9 +/- 3.6) was comparable to that of DBA/1 mice (8.6 +/- 1.9), an H-2(q) strain susceptible for CIA induction. IgG1, IgG2a, and IgG2b antibody responses against CII were elevated in the FcgammaRIIB-deficient animals, especially in those mice showing arthritis, but less pronounced than DBA/1 mice. Histological examinations of the arthritic paws from FcgammaRIIB-deficient mice revealed that cartilage was destroyed and bone was focally eroded in association with marked lymphocyte and monocyte/macrophage infiltration, very similar to the pathologic findings observed in DBA/1 mice. These results indicate that a nonpermissive H-2(b) haplotype can be rendered permissive to CIA induction through deletion of FcgammaRIIB, suggesting that FcgammaRIIB plays a critical role in suppressing the induction of CIA.

Isolation and structural organization of the human preproenkephalin B gene

The primary structure of porcine preproenkephalin B has been elucidated by cloning and sequencing cDNA: it contains neoendorphin, dynorphin and leumorphin (containing rimorphin as its amino-terminus). These opioid peptides, each having a leucine-enkephalin structure, act on the kappa-receptor. We have now cloned a human genomic DNA segment containing the preproenkephalin B gene. The structural organization of this gene resembles those of the genes encoding the other opioid peptide precursors, that is, preproenkephalin A and the corticotropin-beta-lipotropin precursor (ACTH-beta-LPH precursor). The primary structure of human preproenkephalin B has been deduced from the gene sequence. The amino acid sequence homology observed between preproenkephalin B and preproenkephalin A, together with the similarity between their gene organizations, suggests that the two genes have been generated from a common ancestor by gene duplication.

Reexpression of RAG-1 and RAG-2 genes in activated mature mouse B cells

Recombination activating genes (RAG-1 and RAG-2), involved in V(D)J rearrangement of immunoglobulin genes, have been thought to be expressed only in immature stages of B-cell development. However, RAG-1 and RAG-2 transcripts were found to be reexpressed in mature mouse B cells after culture with interleukin-4 in association with several different co-stimuli. Reexpression was also detected in draining lymph nodes from immunized mice. RAG-1 and RAG-2 proteins could be detected by immunofluorescence microscopy in the nuclei of B cells cultured in vitro and in the germinal centers of draining lymph nodes. These findings suggest that RAG gene products play a heretofore unsuspected role in mature B cells.

Primary structure of sheep prostaglandin endoperoxide synthase deduced from cDNA sequence

The complete amino acid sequence of prostaglandin endoperoxide synthase from sheep vesicular gland has been deduced by cloning and sequence analysis of DNA complementary to its messenger RNA. The results were confirmed by digestion of the enzyme with carboxypeptidase Y and by automated Edman degradation of the intact enzyme polypeptide and peptide fragments obtained by limited proteolysis of the enzyme with Achromobacter proteinase I. Mature sheep prostaglandin endoperoxide synthase is shown to be composed of 576 amino acids with an Mr of 66,175. The precursor peptide is predicted to contain a 24-residue signal peptide. The serine residue susceptible to acetylation by aspirin is found to be located near the C-terminus of the enzyme polypeptide.

Requirement of SH2-containing protein tyrosine phosphatases SHP-1 and SHP-2 for paired immunoglobulin-like receptor B (PIR-B)-mediated inhibitory signal

Paired immunoglobulin-like receptor B (PIR-B) (p91) molecule has been proposed to function as an inhibitory receptor in B cells and myeloid lineage cells. We demonstrate here that the cytoplasmic region of PIR-B is capable of inhibiting B cell activation. Mutational analysis of five cytoplasmic tyrosines indicate that tyrosine 771 in the motif VxYxxL plays the most crucial role in mediating the inhibitory signal. PIR-B-mediated inhibition was markedly reduced in the SH2-containing protein tyrosine phosphatases SHP-1 and SHP-2 double-deficient DT40 B cells, whereas this inhibition was unaffected in the inositol polyphosphate 5'-phosphatase SHIP-deficient cells. These data demonstrate that PIR-B can negatively regulate B cell receptor activation and that this PIR-B-mediated inhibition requires redundant functions of SHP-1 and SHP-2.

Cloning, sequencing and expression of cDNA for a novel subunit of acetylcholine receptor from calf muscle

The nicotinic acetylcholine receptor (AChR) from fish electric organ has a subunit structure of alpha 2 beta gamma delta, and this is thought to be also the case for the mammalian skeletal muscle AChR. By cloning and sequencing the complementary or genomic DNAs, we have previously elucidated the primary structures of all four subunits of the Torpedo californica electroplax and calf muscle AChR and of the alpha- and gamma-subunits of the human muscle AChR; the primary structures of the gamma-subunit of the T. californica AChR and the alpha-subunit of the Torpedo marmorata AChR have also been deduced elsewhere. We have now cloned DNA complementary to the calf muscle messenger RNA encoding a novel polypeptide (the epsilon-subunit) whose deduced amino-acid sequence has features characteristic of the AChR subunits and which shows higher sequence homology with the gamma-subunit than with the other subunits. cDNA expression studies indicate that the calf epsilon-subunit, as well as the calf gamma-subunit, can replace the Torpedo gamma-subunit to form the functional receptor in combination with the Torpedo alpha-, beta- and delta-subunits.

Modulation of immunoglobulin (Ig)E-mediated systemic anaphylaxis by low-affinity Fc receptors for IgG

It is widely accepted that immunoglobulin (Ig)E triggers immediate hypersensitivity responses by activating a cognate high-affinity receptor, FcepsilonRI, leading to mast cell degranulation with release of vasoactive and proinflammatory mediators. This apparent specificity, however, is complicated by the ability of IgE to bind with low affinity to Fc receptors for IgG, FcgammaRII and III. We have addressed the in vivo significance of this interaction by studying IgE-mediated passive systemic anaphylaxis in FcgammaR-deficient mice. Mice deficient in the inhibitory receptor for IgG, FcgammaRIIB, display enhanced IgE-mediated anaphylactic responses, whereas mice deficient in an IgG activation receptor, FcgammaRIII, display a corresponding attenuation of IgE-mediated responses. Thus, in addition to modulating IgG-triggered hypersensitivity responses, FcgammaRII and III on mast cells are potent regulators of IgE-mediated responses and reveal the existence of a regulatory pathway for IgE triggering of effector cells through IgG Fc receptors that could contribute to the etiology of the atopic response.

Molecular cloning of a novel murine cell-surface glycoprotein homologous to killer cell inhibitory receptors

We have isolated a cDNA clone encoding a novel murine cell-surface glycoprotein. This polypeptide is predicted to be composed of a signal peptide of 23 amino acids, an extracellular region of 620 amino acids that contains six immunoglobulin-like domains with five potential N-glycosylation sites, a transmembrane sequence of 20 amino acids, and a cytoplasmic tail of 178 amino acids with four sets of sequences similar to the immunoreceptor tyrosine-based inhibition motif. The relative molecular mass of the mature polypeptide is calculated to be 90,520 Da. The polypeptide, designated as p91, shows striking homologies to human killer cell inhibitory receptors, a murine gp49B1 protein, a bovine Fcgamma2 receptor, and a human Fcalpha receptor. The mRNA of p91 was especially abundant in murine macrophages. Western blot analysis using p91-specific anti-peptide sera detected a 130-kDa polypeptide in macrophages. Surface biotinylation and immunoprecipitation analysis verified the surface expression of the translation products on COS-1 cells transfected with the p91 cDNA, but the cells failed to show any Fc binding activity.

Distinct contribution of Fc receptors and angiotensin II-dependent pathways in anti-GBM glomerulonephritis

BACKGROUND

The contribution of antibody and/or immune-complex to the pathogenesis of immunologically-mediated glomerulonephritis is not fully understood, although it has been recently clarified that Fc receptors (FcRs) play critical roles in the inflammatory cascade. We therefore re-evaluated the classical model of glomerulonephritis, anti-glomerular basement membrane antibody-induced glomerulonephritis (Anti-GBM GN), from the standpoint of FcRs and also investigated the residual FcR-independent mechanisms.

METHODS

We adopted an Anti-GBM GN mouse model that has two strains deficient in the FcR gamma chain [gamma(-/-)] or Fc gammaRIIB [RII(-/-)], and analyzed functional (urinary protein, serum creatinine, BUN) and pathological changes of the glomeruli. For the analyses of FcR-independent mechanisms, several doses of nephrotoxic serum were applied, and then mice were treated either with cobra venom factor or an angiotensin II type 1 receptor antagonist in gamma(-/-) mice.

RESULTS

In gamma(-/-) mice, renal injuries were dramatically attenuated with an absence of polymorphonuclear cell (PMN) influx, while RII(-/-) mice suffered accelerated glomerular injuries in spite of a normal PMN influx. In the absence of FcR-dependent effects in gamma(-/-) mice, the FcR-independent pathway lead to chronic renal damage characterized by mesangial proliferation and progressive expansion of mesangial area, with monocyte/macrophage accumulation and with the expression of alpha smooth muscle actin in the mesangial cells and interstitium. Those injuries in gamma(-/-) mice were not attenuated by the decomplementation, but completely abolished by using an angiotensin II type 1 receptor antagonist.

CONCLUSIONS

Our results clearly demonstrate that FcRs play a pivotal role in Anti-GBM GN, especially in its acute phase. We further clarified the existence of FcR and complement-independent but antibody-dependent pathway. Furthermore, we found that those pathological changes were strongly related to the renin-angiotensin system.

Cloning and sequence analysis of the cDNA for arachidonate 12-lipoxygenase of porcine leukocytes

The complete amino acid sequence of arachidonate 12-lipoxygenase (EC 1.13.11.31) of porcine leukocytes was deduced by cloning and sequence analysis of DNA complementary to its mRNA. The sequence was confirmed by automated Edman degradation of the N-terminal regions of the native enzyme and its proteolytic fragments. The cDNA had an open reading frame encoding 662 amino acid residues with a calculated molecular weight of 74,911. Amino acid residues 533-545, Cys-(Xaa)3-Cys-(Xaa)3-His-(Xaa)3-His, showed significant homology to the short cysteine- or histidine-containing sequences proposed as the metal-binding domains of transcription factors and various metal-containing proteins [Berg, J. M. (1986) Science 232, 485-487]. The amino acid sequence of 12-lipoxygenase exhibited 86% identity with human reticulocyte 15-lipoxygenase and showed 41% identity with human leukocyte 5-lipoxygenase. The 12-lipoxygenase cDNA recognized a 3.4-kilobase mRNA species in various porcine cell types, with the largest amount in leukocytes, followed by pituitary, lung, jejunum, and spleen.

Engineering of the major house dust mite allergen Der f 2 for allergen-specific immunotherapy

A major problem with allergen-specific immunotherapy involving repeated injection of allergens is the risk of an anaphylactic reaction. We engineered the major house dust mite allergen, Der f 2, to reduce its capacity to induce skin test reactivity and histamine release from peripheral blood basophils in allergic patients. The engineered allergen, in which the disulfide bond that linked the N- and C-terminal sequences of Der f 2 was disrupted, retained T-cell epitopes essential for immunotherapy and ability to stimulate T-cell proliferation. Such engineered allergens are potentially useful for safer and more effective immunotherapy for allergies.

Mite serine protease activates protease-activated receptor-2 and induces cytokine release in human keratinocytes

BACKGROUND

House dust mites produce serine and cysteine proteases. Mite-derived proteases have been suggested to be involved in the pathogenesis of allergies; however, whether mite-derived serine protease activity can stimulate keratinocytes remains unknown.

METHODS

We examined the activation of primary human keratinocytes by serine protease-rich extract of whole mite culture and compared with that by recombinant group 1 allergens (rDer f 1 and rDer p 1), which exclusively exhibit cysteine protease activity.

RESULTS

Protease activity of whole mite culture extract (WCE), rDer f 1 and rDer p 1 induced the release of IL-8 and granulocyte-macrophage colony-stimulating factor. Protease activity of WCEs induced a significant upregulation of their mRNA expression but rDer f 1 had much less effect. Protease activity of the WCE stimulated intracellular Ca(2+) mobilization but rDer f 1 and rDer p 1 did not. The mobilization induced by agonists for the human protease-activated receptor (PAR)-2, an agonist peptide or trypsin, was diminished by pre-incubation of keratinocytes with WCE. rDer f 1 inefficiently cleaved a synthetic N-terminal peptide of PAR-2 at different sites from trypsin, but the resultant peptides did not stimulate the release of interleukin-8.

CONCLUSIONS

The results suggest that mite-derived serine protease activity may contribute to the pathogenesis of atopic dermatitis by activating keratinocytes via PAR-2 activation but cysteine protease activity of Der f 1 and Der p 1 acts via another mechanism.

Primary structure of delta subunit precursor of calf muscle acetylcholine receptor deduced from cDNA sequence

Clones carrying cDNA sequences for the delta subunit precursor of the acetylcholine receptor from calf skeletal muscle have been isolated. Nucleotide sequence analysis of the cloned cDNA has indicated that this polypeptide consists of 516 amino acids including a hydrophobic prepeptide of 21 amino acids. The delta subunit of the calf muscle acetylcholine receptor, like the alpha, beta and gamma subunits of the same receptor as well as the alpha and gamma subunits of its human counterpart, exhibits structural features common to all four subunits of the Torpedo electroplax receptor, apparently being oriented across the membrane in the same manner as proposed for the fish receptor subunits. The degree of amino acid sequence homology between the calf and Torpedo delta subunits (60%) is comparable to that between the beta subunits (59%) and to that between the gamma subunits (56%), but is lower than that between the alpha subunits of the two species (81%). This suggests that the alpha subunit evolved more slowly than the three other subunits. A dendrogram representing the sequence relatedness among the four subunit precursors of the mammalian and fish acetylcholine receptors has been constructed. Some regions of the delta subunit molecule, including the region containing the putative disulphide bridge and that encompassing the clustered putative transmembrane segments M1, M2 and M3, are relatively well conserved between calf and Torpedo. The relative pattern of regional homology is similar for all four subunit precursors.

Primary structure of gamma subunit precursor of calf-muscle acetylcholine receptor deduced from the cDNA sequence

Clones carrying cDNA sequences for the gamma subunit precursor of the acetylcholine receptor from calf skeletal muscle have been isolated. Nucleotide sequence analysis of the cloned cDNA has revealed the primary structure of this polypeptide, which consists of 519 amino acids including a hydrophobic prepeptide of 22 amino acids. The gamma subunit of the calf muscle acetylcholine receptor, like the alpha subunit of the calf as well as the human muscle receptor, shares features characteristic of all four subunits of the Torpedo electroplax receptor, such as the putative disulphide bridge corresponding to that in the alpha subunit proposed as being in close proximity to the acetylcholine binding site and the four putative, hydrophobic transmembrane segments M1-M4. Thus, the calf gamma subunit molecule apparently exhibits the same transmembrane topology as proposed for the fish receptor subunits. The degree of sequence homology between the calf and Torpedo gamma subunits (56%) is lower than that between the alpha subunits of the two species (81%). Some regions of the gamma subunit molecule, including the region encompassing the putative disulphide bridge and the region containing the putative transmembrane segments M1, M2 and M3, are relatively well conserved between the two species.