Growth-related expression of a double-stranded RNA-dependent protein kinase in 3T3 cells

Cultured mouse 3T3-F442A and 3T3-C2 fibroblasts exhibit a transient double-stranded RNA (dsRNA)-dependent phosphorylation of a 67,000-dalton protein (67K) without prior treatment with interferon (IFN). This phosphoprotein is similar but not identical to the dsRNA-dependent eukaryotic initiation factor-2 (eIF-2) alpha protein kinase (dsI), which regulates protein synthesis in rabbit reticulocytes. We have studied the relationship between cell growth and phosphorylation of the 67K protein (designated 3T3-dsRNA-dependent eIF-2 alpha kinase). A low level of dsRNA-dependent phosphorylation of 3T3-dsI was detectable in extracts prepared from cells not treated with IFN and grown at a low cell density. The phosphorylation of dsI and the phosphorylation of a 38K protein identified as the alpha-subunit (38K) of 3T3-eIF-2 (eIF-2 alpha) occurred concomitantly; the levels of these phosphorylations confluent and thereafter decreased markedly. Treatment of cells with IFN at all stages of growth resulted in an increase in phosphorylation of dsI. 3T3-F442A and 3T3-C2 fibroblasts were found to produce and secrete IFN at levels sufficient to induce an elevated dsI activity.     

Morphological changes of an inflammatory myopathy in rhesus monkeys with simian acquired immunodeficiency syndrome

Eleven of 25 rhesus monkeys which died of simian acquired immunodeficiency syndrome (SAIDS) caused by infection with a type D retrovirus related to Mason-Pfizer monkey virus showed evidence of muscle weakness and atrophy and had elevated levels of muscle enzymes. Biopsies of affected muscle studied with enzyme histochemistry showed the characteristic features of polymyositis. Inflammatory cells consisting of lymphocytes, macrophages, and large vacuolated bizarre-shaped cells of undetermined type were surrounding or invading muscle fibers and were present in the perivascular spaces and endomysia septa. Within the perivascular infiltrates, lymphocytes were abundant but very few macrophages were present. Other myopathic features including profound proliferation of fibrous tissue, necrosis, and phagocytosis of muscle fibers were noted to a variable degree. The retrovirus was isolated from affected muscles. The clinical and historical features of polymyositis in rhesus monkeys with SAIDS are very similar to those of human polymyositis. The polymyositis in SAIDS induced by a type D retrovirus related to Mason-Pfizer monkey virus is an excellent primate model to study the mechanism and morphological changes of viral-induced muscle damage.     

Infection of macaque monkeys with simian immunodeficiency virus from African green monkeys: virulence and activation of latent infection

The virulence of three isolates of simian immunodeficiency virus from African green monkeys (SIVagm) was studied in rhesus and pigtailed macaques. None of 15 rhesus monkeys and one of four pigtailed monkeys died from infection during the time they were studied (up to 33 months). SIVagm was only isolated from rhesus monkeys for up to 2 months after inoculation. However, when these animals were secondarily infected with Simian acquired immunodeficiency syndrome retrovirus type 1 (SRV-1), SIVagm was activated and isolated. Dual infection caused increased mortality.     

Characterization of cDNA clones for human glycophorin A. Use for gene localization and for analysis of normal of glycophorin-A-deficient (Finnish type) genomic DNA

Glycophorin A is the major membrane sialoglycoprotein of human erythrocytes and represents a typical example of a transmembrane glycoprotein. The functional role of this cell-surface component is not known but it represents a receptor for viruses, bacteria and parasites like Plasmodium falciparum. 1. Two cDNA clones encoding glycophorin A have been characterized from human fetal cDNA libraries. The longer cDNA extended from the coding region of glycophorin A (residues 4-131) to the 3' untranslated region which included two polyadenylation signals and a poly(A) tail. 2. The structural gene for glycophorin A is located on chromosome 4, q28-q31 as shown by in situ hybridization, thus confirming the previous localization by genetic linkage analysis. 3. Three distinct mRNA species (1.0 kb, 1.7 kb and 2.2 kb) have been identified in erythroid spleen. Northern blot analyses with a probe directed against the 3' untranslated region of the mRNAs indicated that all these species share a homologous 3' non-coding region and that the first polyadenylation signal downstream the stop codon is not used. 4. Preliminary studies by Southern blot analysis of the genomic DNA from normal En(a+) and rare En(a-) donors suggest that the glycophorin A gene has a complex organization and is largely deleted in donors of the En(a-) phenotype (Finnish type) who lack glycophorin A on their red cells.     

Measurement of cytosolic free magnesium ion concentration by 19F NMR

Fluorinated derivatives of the chelator o-aminophenol-N,N,O-triacetic acid (APTRA) have been developed, synthesized, and analyzed for use as 19F NMR indicators of free cytosolic magnesium concentration. Magnesium dissociation constants for the 4-fluoro, 5-fluoro, and 4-methyl-5-fluoro species were determined to be 3.1, 0.9, and 0.6 mM, respectively, on the basis of UV absorption measurements at 37 degrees C in 115 mM KCl and 20 mM NaCl, pH 7.1, buffered with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid-tris-(hydroxymethyl)aminomethane. The corresponding pK values, which reflect protonation of the nitrogen atom, were determined by 19F NMR to be 4.15, 5.45, and 5.55, respectively, so that the chelators are insensitive to pH variations near the normal physiological range. The dissociation constants of these chelators for calcium ions are lower than those for magnesium but roughly 2-3 orders of magnitude above typical basal cytosolic free calcium levels, so that calcium ions will not interfere with the determinations of magnesium levels. 19F NMR studies carried out at 339.7 MHz indicate that magnesium ions are in slow exchange with the 5-fluoro and 4-methyl-5-fluoro APTRA derivatives and in fast exchange with the 4-fluoro APTRA derivative. In contrast, calcium ions were found to be in intermediate to fast exchange with all chelators. The apparent anomaly of higher thermodynamic stability of the APTRA complexes for calcium relative to magnesium but lower kinetic stability (higher k-1 values) for the calcium complexes reflects the very different association rates for the two ions. Thus, the magnesium association rates are 3 orders of magnitude slower than those for calcium ions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation of cDNA clones and complete amino acid sequence of human erythrocyte glycophorin C

Two cDNA clones for glycophorin C, a transmembrane glycoprotein of the human erythrocyte which carries the blood group Gerbich antigens, have been isolated from a human reticulocyte cDNA library. The clones were identified with a mixture of 32 oligonucleotide probes (14-mer) which have been synthetized according to the amino acid sequence Asp-Pro-Gly-Met-Ala present in the N-terminal tryptic peptide of the molecule. The primary structure of glycophorin C deduced from the nucleotide sequence of the 460 base-pair insert of the pGCW5 clone indicates that the complete protein is a single polypeptide chain of 128 amino acids clearly organized in three distinct domains. The N-terminal part (residues 1-57, approximately) which is N- and O-glycosylated is connected to a hydrophilic C-terminal domain (residues 82-128, approximately) containing 4 tyrosine residues by a hydrophobic stretch of nonpolar amino acids (residues 58-81, approximately) probably interacting with the membrane lipids and permitting the whole molecule to span the lipid bilayer. Northern blot analysis using a 265-base-pair restriction fragment obtained by DdeI digestion of the inserted DNA shows that the glycophorin C mRNA from human erythroblasts is approximately 1.4 kilobases long and is present in the human fetal liver and the human K562 and HEL cell lines which exhibit erythroid features. The glycophorin C mRNA, however, is absent from adult liver and lymphocytes, indicating that this protein represents a new erythrocyte-specific probe which might be useful to study erythroid differentiation.