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PubMedDate not supplied

[Participation of cytoplasmic factors in the rate of transcription in compensatory hyperfunction of the heart].

Effect of cytoplasmic fraction S-100 from normal heart and liver tissue as well as from the tissues at the period of compensatory growth, caused by hyperfunction, on the rate of transcription in isolated nuclei was studied. In normal state heart and liver cytoplasm contained factors, accelerating RNA synthesis in nuclei, while activity of RNA-polymerase I was increased most significantly in presence of these factors as compared with RNA-polymerase II. Activity of these cytoplasmic factors, accelerating transcription, was distinctly increased in heart hyperfunction and in the liver tissue remaining after partial hepatectomy. The heart and liver cytoplasmic factors proved to be of protein nature, they did not exhibit any tissue specificity and their activity correlated with the rate of cellular RNA synthesis. Activation of cytoplasmic protein factors, accelerating transcription, appears to be an important mechanism, initiating the RNA synthesis increase in response to elevation of a tissue physiological functions.

Animals↗
PubMedDate not supplied

[Does Masui's Ca-sensitive cytostatic factor exist in the cytoplasm of mature nonactivated eggs of Acipenser stellatus, Rana temporaria and Xenopus laevis?].

The cytoplasm of mature non-activated and cleaving eggs of A. stellatus and R. temporaria had no cytostatic effect. The cytoplasm treated with EGTA, being injected in one of two blastomeres of the cleaving egg of the same species, inhibits fully or partially the cleavage. The nuclei in the "arrested" blastomeres had, however, vesicular structure but were not blocked at metaphase, as could be expected if the cleavage was inhibited by a cytostatic factor described by Masui (1974). The portion of perished embryos and "arrested" blastomeres was shown to increase with the dose of EGTA injected in the egg, donor of cytoplasm. In the experiments with reciprocal injections of the intact cytoplasm of the mature non-activated eggs in one of two blastomeres of the recipient embryo carried out on R. temporaria and X. laevis, the cytoplasm of X. laevis only arested the cleavage but in this case as well only 4 out of 32 "arrested" blastomeres were at metaphase. The cytostatic effect observed in our experiments was not, hence, similar to that observed by Masui on R. pipiens.

Animals↗
PubMed1984

Effect of hemin on poly (A)-containing RNA synthesis and transport from nucleus into cytoplasm in Friend cells of the Fw line.

The effect of hemin on the transcription and post-transcriptional events (processing and transport of globin mRNA and other poly(A)-containing RNAs to the cytoplasm) was investigated in murine erythroleukemia Friend cells (MELC) of the Fw line. Uninduced Fw cells or Fw cells induced to differentiation by butyric acid were incubated in vitro without or with exogenous hemin. Short labelling periods (5-20 min) with (3H) uridine were used. The synthesis of globin mRNA and other poly(A)-containing RNAs at the level of their precursors in the nucleus and at the level of mature forms in the cytoplasm was measured. Our results indicate that hemin mainly affects the processing or transport of globin mRNA and other poly(A)-containing RNAs from the nucleus to the cytoplasm. The effect of exogenous hemin is quite different in uninduced and induced Fw cells. Exogenous hemin stimulates accumulation of poly(A)-containing RNA in nuclei of uninduced Fw cells. On the other hand exogenous hemin causes an increase in cytoplasmic globin mRNA and other cytoplasmic poly(A)-containing RNA in Fw cells induced by sodium butyrate.

Animals↗
PubMed1983

Phaseolus vulgaris cytoplasmic leucyl-tRNA synthetase. Purification and comparison of its catalytic, structural, and immunological properties with those of the chloroplastic enzyme.

The cytoplasmic leucyl-tRNA synthetase was purified from bean (Phaseolus vulgaris) leaves. After ammonium sulfate fractionation and chromatography on Sephadex G-50, DEAE-cellulose, hydroxylapatite, and phosphocellulose, complete purification was achieved by blue Sepharose CL-6B chromatography using specific elution with pure yeast tRNALeu1. The enzyme was purified 1050-fold and had a specific activity of 940 nmol of leucyl-tRNA formed/min/mg of protein. Polyacrylamide gel electrophoresis of the native enzyme showed one band, but the denatured enzyme showed two bands. These two protein bands are structurally related. The smallest protein appears to be a cleavage product from the largest one, suggesting the presence of a sensitive cleavage site in the cytoplasmic leucyl-tRNA synthetase. The cytoplasmic enzyme is a monomer (Mr = 130,000), larger than its chloroplastic counterpart (Mr = 120,000). The two enzymes differ in their substrate (tRNA) specificity, tryptic peptide map, and amino acid composition. Antibodies were raised against the cytoplasmic enzyme and against the chloroplastic enzyme and no cross-immunological reaction was detected, showing that the two enzymes do not share any antigenic determinant. Taken together, these results suggest that P. vulgaris cytoplasmic and chloroplastic leucyl-tRNA synthetases are coded for by different genes.

Amino Acids↗
PubMed1983

Spread of Balbiani ring derived messenger RNA in Chironomus salivary gland cell cytoplasm.

We have investigated whether Balbian ring derived mRNA (75S RNA) of Chironomus salivary glands spreads to the different parts of the cytoplasm before or after attachment to the rough endoplasmic reticulum. Glands were fixed after in vivo administration of tritiated uridine and cytidine and the appearance of labelled RNA fractions in microdissected cytoplasm was measured. We chose central cytoplasm rich in rough endoplasmic reticulum (endoplasm) and peripheral cytoplasm with a low content of reticulum (basal zone). A peripheral spread of the mRNA on reticulum membranes would have moved the labelled RNA outwards with time. We found, however, a redistribution in the opposite direction, suggesting that the mRNA spreads over the whole cytoplasm before it attaches to the reticulum membranes. A similar redistribution occurs for the ribosomal subunits.

Animals↗
PubMed1982

[New Djungarian hamster cell lines with selective cytoplasmic and nuclear genetic markers].

Two new Djungarian hamster cell lines which are resistant to chloramphenicol (CAP) are described. The clonal DMCAP subline was obtained by incubation of HPRT-deficient DM-15 cells for 6 months in the medium containing 50 micron/ml of CAP. Resistance to CAP is determined in DMCAP cells by the cytoplasm: cytoplasts from these cells could transmit resistance to CAP into sensitive cells, such as L or DMCH-2/1 cells by hybridization. However, after transplantation of DMCAP nuclei into L cytoplasts, the resulting hybrid cells lost resistance to CAP to a great extent. Using the capacity of DMCAP cytoplasts to transfer CAP-resistance, we obtained a line of hybrids (cyt. DMCAP X DMCH-2/1) which was resistant to 8-azaguanine, CAP and colchicine. As in the original DMCH-2/1 cell line, colchicine-resistance in the cybrid line appeared to be associated with gene amplification. Thus, chromosomal analysis showed that the karyotype of the hybrids was identical to that of DMCH-2/1 cells. Both contained marker chromosomes with homogeneously staining regions (HSRs) and, during incubation in the colchicine-free medium, lost resistance to colchicine. The loss of resistance was accompanied by a decrease in the number of cells containing chromosomes with HSRs and an increase in the number with double minutes (DMs). Many cells containing small chromatin bodies in their cytoplasm also appeared. These chromatin bodies may be DMs lost from the nucleus during mitosis. These new sublines with cytoplasmic and nuclear genetic markers may be useful in the further study of cytoplasmic-nuclear interactions, particularly, in the analysis of possible activities of the DNA fragments which appear in the cytoplasm during reversion to colchicine sensitivity.

Animals↗
PubMed1982

Evidence for turnover of DNA in the nucleus and in the cytoplasm of adult post-mitotic neurons in vivo.

Experiments were designed to determine if turnover of DNA occurs in post-mitotic neurons of adult mammals. Three-month-old laboratory mice, Mus musculus, and white footed mice, Peromyscus leucopus, were given three injections of 3H-thymidine (3H-TdR, 16 muCi/g body weight) at noon, 4 pm and 8 pm, and were killed serially beginning 1 h after the last injection. The brain stem was removed from the animals and autoradiographed. Some of the sections were treated with DNase prior to autoradiography. A sensitive and accurate method of autoradiographic grain count analysis was used to measure the grain counts over areas of neuron nuclei, neuron cytoplasm and background areas of the slide (Cameron, Pool and Hoage, 1979). There was a significant elevation of grains per unit area above background over both the nucleus and the cytoplasm in animals killed 24 h after the last 3H-TdR injection. Counts were reduced to background level by prior DNase treatment. This shows that the grains over the nucleus and the cytoplasm were due to label in the DNA. Changes in the grain counts with time were subjected to least squares regression analysis. In the mouse both the nucleus and the cytoplasmic grain counts showed a decreasing slope which was significantly different from a slope of zero when the data were fitted to either a linear model or a log-linear model. The data showed a somewhat better fit to the log-linear model. The labelled nuclear DNA in the mouse had a calculated half-life of about 502 h while the labelled cytoplasmic DNA had a calculated half-life of about 97 h. Our ability to measure and to characterize DNA turnover in specific in vivo cell types allows us to test theories about its functional role.

Animals↗
PubMed1981

[Interrelation between protein synthesis and nucleo-cytoplasmic transport of messenger RNA in cells of rat livers in different stages of regeneration].

Synthesis of nonribosomal RNA was increased 2-2.5-fold in nuclei of rat liver cells at early steps of regeneration /2 days after partial hepatectomy/under conditions of protein synthesis inhibition by means of cycloheximide within 3 hrs. Amount of mRNA, transferred from nuclei into cytoplasm, was also 2-fold higher under these conditions as compared with control cells. The mRNA, transferred from nuclei into cytoplasm under the conditions of cycloheximide treatment of liver cells at early steps of regeneration, did penetrate the polyribosomes although the protein synthesis did not occur on the polyribosomes formed. At the later steps of regeneration /within 5 days after partial hepatectomy/ under the conditions of protein synthesis inhibition by cycloheximide within 3 hrs, formation of nonribosomal RNA was decreased by 40% in liver cell nuclei; amount of mRNA, transferred into cytoplasm, was also decreased by 40%. When the cycloheximide treatment was carried out during 1 hr, synthesis of nonribosomal RNA was increased 1.5-fold in liver cell nuclei at the later steps of regeneration although the amount of mRNA, transferred from nuclei into cytoplasm, was decreased by 30% as compared with the control cells. The data obtained suggest that during rat liver tissue regeneration a change occurred in the molecular mechanisms linking translation, biosynthesis and nuclear-cytoplasmic transport of mRNA of "tumoral" type/at early steps of regeneration/ or "normal type"/ at later steps of regeneration.

Animals↗
PubMed1993

Mapping of the alpha-actinin binding site within the beta 1 integrin cytoplasmic domain.

The actin cross-linking protein alpha-actinin binds to the cytoplasmic domain of the beta 1 subunit of integrin, suggesting that alpha-actinin may form a direct link between the actin cytoskeleton and the transmembrane fibronectin receptor. In this study, we have used short synthetic peptides to localize the binding site for alpha-actinin within the cytoplasmic domain of beta 1 integrin. Four 13-residue peptides were tested in both an affinity chromatographic assay and a solid-phase binding assay. The results indicated that two regions of sequence contribute to the binding of alpha-actinin: one near where the beta 1 cytoplasmic tail emerges from the membrane and a second segment located near the C terminus of the cytoplasmic tail. This binding pattern was investigated in more detail using an adaptation of the mimotope assay, in which each of the 32 overlapping sequential decapeptide segments from the beta 1 cytoplasmic domain was assembled on the head of a different plastic pin. The peptide-pin constructs were used to detect the binding of 125I-alpha-actinin. As predicted from our initial results, alpha-actinin was found to bind to two distinct clusters of peptide segments. This represents a novel use of the mimotope pin assay to map interactive sites on structural proteins.

Actinin↗
PubMed1995

Chimeric proteins containing the cytoplasmic domains of the mannose 6-phosphate receptors codistribute with the endogenous receptors.

We have constructed and transiently expressed in HeLa cells a series of hybrid proteins in which the cytoplasmic domain or both the transmembrane and the cytoplasmic domains of the mannose 6-phosphate/insulin-like growth factor II receptor were fused to the ectodomain of the hemagglutinin of the influenza virus (HA), a typical plasma membrane protein. In addition, we have expressed a hybrid protein containing the luminal domain of HA fused to the transmembrane and cytoplasmic tail of the cation-dependent mannose 6-phosphate receptor. These hybrids were transported through and sorted from the secretory pathway as shown by acquisition of endo-H resistant oligosaccharides and their ability to recruit the Golgi assembly proteins AP-1 on the Golgi membrane. Like the mannose 6-phosphate receptors (MPRs), these hybrid proteins are also present in small amounts at the cell surface where they are likely to undergo endocytosis as disruption of the endocytosis signals contained in the MPR cytoplasmic domains induces their accumulation at the cell surface. Double immunofluorescence studies indicate that these chimeras codistribute with the endogenous MPRs at steady state. The results suggest that the cytoplasmic domains of the MPRs are sufficient to determine the steady-state distribution of the full-length proteins.

Base Sequence↗
PubMed1995

Characterization of sorting signals in the beta-amyloid precursor protein cytoplasmic domain.

The beta-amyloid precursor protein (APP) is proteolytically processed to generate beta-amyloid protein, the principal protein component of neuropathological lesions characteristic of Alzheimer's disease. To investigate potential sorting signals in the cytoplasmic tail of APP, we transplanted APP cytoplasmic tail sequences into the cytoplasmic tail of the human transferrin receptor (TR) and showed that two sequence motifs from the APP cytoplasmic tail promote TR internalization. One sequence, GYENPTY, is related to the low density lipoprotein receptor internalization signal, FDNPVY, but also involves a critical glycine residue; the other, YTSI, conforms to the 4-residue tyrosine-based internalization signal consensus sequence. Furthermore, a chimeric molecule (APP-TR) consisting of the cytoplasmic domain of APP and the transmembrane and external domains of TR was rapidly internalized enabling the transport of iron into the cell at approximately 50% the rate of wild-type TR. Alanine scanning mutations indicated that the two sequences identified in transplantation experiments were required for internalization of the chimera. Metabolic pulse-chase experiments showed that the APP-TR chimeras were degraded in a post-Golgi membrane compartment within 2-4 h following normal glycosylation. Degradation was partially dependent upon the two internalization signals and was inhibited by ammonium chloride. A fraction of APP-TR chimeras traffic to a degradative endocytic compartment after appearing on the cell surface. Comparison of soluble APP released from cells expressing either full-length human APP or mutant APP with the sequence YENPTY deleted indicated that this sequence is required for sorting of full-length APP along similar trafficking pathways as the APP-TR chimera.

Amino Acid Sequence↗
PubMed1994

Cytoplasmic p105 index is an accurate mitotic index, but is not related to prognosis in cervical carcinoma.

The monoclonal antibody p105 (clone 780-3) recognizes proliferation-associated nuclear antigen p105 in conventionally fixed and processed histological materials. Formaldehyde solution-fixed and paraffin-embedded specimens excised from 184 patients with stage III squamous cell carcinoma of the cervix who were treated with radiation therapy alone were investigated for p105 positivity using an immunohistochemical method. Mitotic cancer cells were strongly positive for p105, showing cytoplasmic p105 positivity in almost all cases. The mean cytoplasmic p105 index was 2.02%, and the mean mitotic index in hematoxylin-eosin-stained preparations was 0.65%. There was a correlation between the cytoplasmic p105 index and mitotic index in hematoxylin-eosinstained preparations (y = 0.32x-0.003, r = .63). There was no significant relationship between the cytoplasmic p105 index or mitotic index in hematoxylin-eosin-stained preparations and prognosis. These results indicate that the cytoplasmic p105 index is not a predictive indicator for prognosis in patients with cervical squamous cell carcinoma, although this index is a more accurate mitotic index than the mitotic index itself in hematoxylin-eosin-stained preparations.

Adult↗
PubMed1994

Antineutrophil cytoplasmic autoantibody-associated alveolar capillaritis in patients presenting with pulmonary hemorrhage.

The objective of this study was to determine the significance of the antineutrophil cytoplasmic autoantibodies (ANCAs) from the clinicopathologic viewpoint of pulmonary hemorrhage occurring as a prominent event of disease. Forty-three consecutive patients with both pulmonary hemorrhage as a prominent clinical manifestation and a positive test for antineutrophil cytoplasmic autoantibodies were studied. Thirty-six patients underwent open lung biopsy, including histologic, tissue immunofluorescence, and microbiologic studies. Immunoassays were performed to investigate the antigenic specificities of antineutrophil cytoplasmic autoantibodies in the patients studied. All patients with lung biopsy confirmation had pauci-immune hemorrhagic alveolar capillaritis as the main morphologic substrate. In addition, renal involvement in the form of pauci-immune crescentic glomerulonephritis was a common finding. Serum samples from the 43 study patients contained antibodies that were monospecific for proteinase 3 (n = 13) or myeloperoxidase (n = 30). In our study, whereas anti-proteinase 3 antibodies were mainly detected in patients with alveolar capillaritis and a well-established diagnosis of Wegener's granulomatosis, antimyeloperoxidase antibodies were principally found in those patients who had alveolar capillaritis and polyarteritis nodosa not only as a primary finding but also accompanying other diseases. However, a significant number of patients with alveolar capillaritis and antimyeloperoxidase antibodies showed no evidence of polyarteritis nodosa (idiopathic pulmonary-renal syndrome and isolated forms of pulmonary hemorrhage). We conclude that in patients presenting with pulmonary hemorrhage as a prominent event of disease, antineutrophil cytoplasmic autoantibodies are a new clue strongly supportive of a pulmonary capillary vasculitis, irrespective of the primary underlying disease. Moreover, the antigenic subtype of antineutrophil cytoplasmic autoantibodies helps in recognizing the type of vasculitic disorder involved.

Antibodies↗
PubMedDate not supplied

Double-stranded RNA of homothallic Saccharomycetes with different cytoplasmic determinants of antagonistic activity.

Double-stranded RNA of high molecular weight is found in the cytoplasm of the "killer" strain M-437-2. The RNA is homogeneous and contains no single strand poly(A) portions. The double-stranded RNA is associated with the cytoplasmic microsomes of strain M-437-2 and is contained in the fraction of the cell contents of this strain that was used to infect germinating spores of the sensitive S. cerevisiae 768(1)-15 with the cytoplasmic determinant [k]. The absence of this RNA in cells of the initial sensitive strain 768(1)-15, and its appearance in the "killer" derivative of this strain produced by infection with the determinant [k] by means of the above-mentioned fraction, indicate that the killer activity is due to the double-stranded RNA. The retention of the double-stranded RNA in the cytoplasm of derivatives of the newly-formed killer strain, containing the cytoplasmic determinants [k(ts)] and [n] suggests also that these determinants are a modification of determinant [k].

Cytoplasm↗
PubMed1994

Cytoplasmic localization of the mitogen-activated protein kinase activator MEK.

The mitogen-activated protein kinase (MAPK) or extracellular signal-regulated kinase (ERK) is phosphorylated and activated by an upstream activator kinase, MEK (MAPK or ERK kinase), in response to mitogenic growth factors. ERKs translocate into the nucleus upon mitogen stimulation, suggesting that the subcellular redistribution of ERK may play a critical role in signal transfer from cytoplasm to the nucleus. We demonstrated in this report that MEK was exclusively localized in cytoplasm in several cell lines, including Swiss 3T3, HeLa, COS, and PC12. Immunofluorescence analysis of both native and transiently expressed MEK with a MEK-specific antibody revealed that both MEK1 and MEK2 were localized only in the cytoplasm. The cytoplasmic localization of MEK was further supported by subcellular fractionations as well as detergent permeabilization experiments. In contrast to ERK, mitogen stimulation did not cause any nuclear accumulation of MEK. These data suggest that ERK is phosphorylated and activated in the cytoplasm. The activated ERK could subsequently translocate into the nucleus and phosphorylate its nuclear substrates.

3T3 Cells↗
PubMed1994

Cytoplasmic and surface membrane phenotypic markers in cells of B cell chronic lymphocytic leukemia.

Peripheral blood cells of twenty-six patients with B cell chronic lymphocytic leukemia (B-CLL) were characterized for their surface membrane and cytoplasmic marker profiles using flow cytometry and fluorescence microscopy. According to surface membrane marker analysis three distinct immunophenotypic subgroups of B-CLL were identified: group I (SIg+, MR+, CD5+, B Ag+, T Ag-; 19 cases), group II (SIg+, MR+, CD5+, B Ag+, TAg+; 3 cases), group III (SIg-, MR+, CD5+, B Ag+, T Ag-; 4 cases). Cells from all patients were positive for the CD19 antigen and at least one of other B cell antigens. Cells from all patients expressed also CD5 and HLA-DR antigens and formed mouse rosettes (MR). Great heterogeneity was found in the membrane and cytoplasmic marking by anti-CD22 MoAb. In four of 23 patients tested, CD22 antigen was expressed in the cytoplasm of CLL cells while it was absent on surface membrane of these cells. This finding was discussed from the point of certain cell heterogeneity in the followed B-CLL cases. Cytoplasmic immunoglobulin (CyIg) detection showed to be very important especially in group III of followed B-CLL cases with undetectable surface immunoglobulins (SIg). Cytoplasmic antigens and immunoglobulin determinations are useful in phenotyping every B-CLL patient, as well as in the immunological study of different maturation stages of B lymphocytes.

Aged↗
PubMed1993

Human granulocyte-macrophage colony-stimulating factor receptor signal transduction requires the proximal cytoplasmic domains of the alpha and beta subunits.

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) controls the production, maturation, and function of cells in multiple hematopoietic lineages. These effects are mediated by a cell-surface receptor (GM-R) composed of alpha and beta subunits, each containing 378 and 881 amino acids, respectively. Whereas the alpha subunit exists as several isoforms that bind GM-CSF with low affinity, the beta common subunit (beta c) does not bind GM-CSF itself, but acts as a high-affinity converter for GM-CSF, interleukin-3 (IL-3), and IL-5 receptor alpha subunits. The cytoplasmic region of GM-R alpha consists of a membrane-proximal conserved region shared by the alpha 1 and alpha 2 isoforms and a C-terminal variable region that is divergent between alpha 1 and alpha 2. The cytoplasmic region of beta c contains membrane proximal serine and acidic domains. To investigate the amino acid sequences that influence signal transduction by this receptor complex, we constructed a series of cytoplasmic truncation mutants of the alpha 2 and beta subunits. To study these truncations, we stably transfected the IL-3-dependent murine cell line Ba/F3 with wild-type or mutant cDNAs. We found that the wild-type and mutant alpha subunits conferred similar low-affinity binding sites for human GM-CSF to Ba/F3, and the wild-type or mutant beta subunit converted some of these sites to high-affinity; the cytoplasmic domain of beta was unnecessary for this high-affinity conversion. Proliferation assays showed that the membrane-proximal conserved region of GM-R alpha and the serine-acidic domain of beta c are required for both cell proliferation and ligand-dependent phosphorylation of a 93-kD cytoplasmic protein. We suggest that these regions may represent an important signal transduction motif present in several cytokine receptors.

Amino Acid Sequence↗
PubMed1993

Role of the mu immunoglobulin heavy chain transmembrane and cytoplasmic domains in B cell antigen receptor expression and signal transduction.

Membrane immunoglobulins (mIg) serve as the recognition components of B lymphocyte antigen receptors. Binding of antigen to these receptors leads to dramatic effects on B cell growth and viability. We have examined the structural elements of mIgM that are involved in antigen receptor assembly and function. Expression of transfected wild-type mIgM in a B cell line led to assembly with the other two known components of the antigen receptor, Ig-alpha and Ig-beta, expression on the cell surface, and when cross-linked by anti-IgM antibodies, stimulation of signal transductin reactions, including tyrosine protein phosphorylation, inositol phosphate production, and increases in cytoplasmic calcium concentration. Replacement of the highly conserved COOH-terminal 41 amino acids of mIgM heavy chain (mu m) with the transmembrane and cytoplasmic domains of human CD8 alpha resulted in a molecule which was expressed on the B cell surface at levels comparable to wild-type mIgM, but which did not form a complex with Ig-alpha or Ig-beta and did not stimulate any of the signaling reactions mentioned above. Replacement of the basic three-amino-acid cytoplasmic domain of mu m with a different but similarly charged sequence had no effect on cell-surface expression or signaling function. On the other hand, removal of the entire cytoplasmic domain resulted in a molecule which did not bind Ig-alpha and Ig-beta and which did not transduce signals. This effect is probably due to altered post-translational processing of this mutant molecule. Finally, a series of eight single-amino-acid substitutions in the transmembrane domain was constructed. Most of these resulted in the removal of hydroxyl groups from conserved residues postulated to be important for interactions with other components. Each of these mutant molecules was capable of transducing signals when cross-linked by anti-IgM, but one was partially defective. Since alteration of any single residue was not sufficient to disrupt signaling completely, the interactions required for signaling are likely to involve multiple residues, so that elimination of one hydroxyl group does not prevent the interaction. We propose that the cytoplasmic domain of mu m does not play a critical role in receptor function but that the transmembrane domain specifies interactions with other components, probably Ig-alpha and Ig-beta, required for proper antigen receptor signal transduction.

Animals↗