The structural biology of CD2.

The CD2 molecule is a 50-55KD transmembrane glycoprotein expressed on the vast majority of thymocytes and virtually all peripheral T lymphocytes. Its functions are two-fold: adhesion and activation. CD2 serves to facilitate conjugate formation between the T-lineage cell and its cognate partner via intermolecular interaction of CD2 and LFA-3 on the former and latter cells, respectively.

Identification of human CD4 residues affecting class II MHC versus HIV-1 gp120 binding.

Interactions of CD4 with the class II major histocompatibility complex (MHC) are crucial during thymic ontogeny and subsequently for helper and cytotoxic functions of CD4+CD8- T lymphocytes. CD4 is the receptor for the T-lymphotropic human immunodeficiency virus and binds its envelope glycoprotein, gp120. The residues involved in gp120 binding have been localized to a region within the immunoglobulin-like domain I of CD4, which corresponds to CDR2 of an immunoglobulin variable region, but the CD4 residues important in MHC class II interaction have not been characterized.

Role of bile acid conjugation in hepatic transport of dihydroxy bile acids.

The effect of conjugation and side chain length on dihydroxy bile acid unidirectional hepatic uptake and efflux was studied using the isolated perfused rat liver which was perfused prograde or retrograde in single pass fashion. Deoxycholic acid (DC) and its C23 (nor) derivative nor-DC, as well as the synthetically prepared taurine conjugate of DC, were administered at a constant dose of 1 mumol/min/kg (body weight), upon which a bolus tracer dose of labeled bile acid was superimposed. Analysis of radioactivity recovery in perfusate indicated that unidirectional uptake of all three bile acids was equally rapid, but that only nor-DC showed considerable and continuing efflux into the perfusate; this involved mostly the unchanged acid.

Activation of the trk oncogene by alternatively spliced muscle and non-muscle tropomyosin sequences.

We have constructed a derivative of the trk oncogene in which the cytoskeletal tropomyosin sequences are replaced with skeletal muscle alpha-tropomyosin sequences derived from the same tropomyosin gene by alternative splicing. The biochemical and biological properties of this derivative are indistinguishable from those of the naturally occurring trk oncogene. Thus activation of the oncogenic activity of trk is a function of structural features of tropomyosin which are common to both skeletal muscle and non-muscle isoforms.

Successful use of clozapine in a patient with a history of neuroleptic malignant syndrome.

Reinstitution of antipsychotic medication is problematic in patients with a history of neuroleptic malignant syndrome (NMS). In this case, a patient with a history of probable neuroleptic malignant syndrome caused by administration, as single agents, of haloperidol, molindone, and lithium was later treated successfully with the novel antipsychotic clozapine. The propensity of various antipsychotic agents to cause NMS is discussed.

Expression of a functional CD3-Ti antigen/MHC receptor in the absence of surface CD2. Analysis with clonal Jurkat cell mutants.

To investigate the requirement for CD2 expression in activation of T lymphocytes via the CD3-Ti antigen/MHC receptor complex, we produced and characterized a series of CD2- Jurkat variants. These mutants lack detectable surface CD2 as determined by indirect immunofluorescence, immunoprecipitation analysis, and specific radiolabeled antibody binding assay, but nevertheless, expressed normal numbers of CD3-Ti receptors. As expected, the combination of anti-CD2 antibodies, termed anti-T112 and anti-T113, which are mitogenic for resting T lymphocytes, failed to stimulate activation of these variants.

Substitution of murine for human CD4 residues identifies amino acids critical for HIV-gp120 binding.

Human CD4 is the receptor for the gp120 envelope glycoprotein of human immunodeficiency virus and is essential for virus entry into the host cell. Sequence analysis of CD4 has suggested an evolutionary origin from a structure with four immunoglobulin-related domains. Only the two NH2-terminal domains are required to mediate gp120 binding.

Molecular cloning of the common acute lymphoblastic leukemia antigen (CALLA) identifies a type II integral membrane protein.

Common acute lymphoblastic leukemia antigen (CALLA) is a 100-kDa cell-surface glycoprotein expressed on most acute lymphoblastic leukemias and certain other immature lymphoid malignancies and on normal lymphoid progenitors. The latter are either uncommitted to B- or T-cell lineage or committed to only the earliest stages of B- or T-lymphocyte maturation. To elucidate to homogeneity, obtained the NH2-terminal sequence from both the intact protein and derived tryptic and V8 protease peptides and isolated CALLA cDNAs from a Nalm-6 cell line lambda gt10 library using redundant oligonucleotide probes.

Interdependence of CD3-Ti and CD2 activation pathways in human T lymphocytes.

Human T lymphocytes can be activated through either the antigen/MHC receptor complex T3-Ti (CD3-Ti) or the T11 (CD2) molecule to proliferate via an IL-2 dependent mechanism. To investigate the relationship of these pathways to one another, we generated and characterized Jurkat mutants which selectively express either surface CD3-Ti or CD2. Here we show that CD3-Ti- mutants fail to be stimulated by either pathway to increase phosphoinositide turnover, mobilize calcium or induce the IL-2 gene.

Organization of the hTMnm gene. Implications for the evolution of muscle and non-muscle tropomyosins.

We have isolated clones of human genomic DNA which contain the structural elements of the hTMnm gene. In non-muscle tissue this gene produces a 2.5 kb (1 kb = 10(3) bases or base-pairs) mRNA encoding TM30nm, a 248 amino acid cytoskeletal tropomyosin.

The gene for T11 (CD2) maps to chromosome 1 in humans and to chromosome 3 in mice.

The chromosomal locations of the human and murine T11 (CD2) gene have been determined. Using recently cloned cDNA to probe Southern blots of mouse X human and Chinese hamster X mouse somatic cell hybrids, we have localized the human T11 gene to chromosome 1 and the murine T11 gene to chromosome 3. Based on previously determined blocks of homology between human chromosome 1 and mouse chromosome 3, it is suggested that the human T11 gene may lie on the short arm of chromosome 1 proximal to p221.

Exon-intron organization and sequence comparison of human and murine T11 (CD2) genes.

Genomic DNA clones containing the human and murine genes coding for the 50-kDa T11 (CD2) T-cell surface glycoprotein were characterized. The human T11 gene is approximately equal to 12 kilobases long and comprised of five exons. A leader exon (L) contains the 5'-untranslated region and most of the nucleotides defining the signal peptide [amino acids (aa) -24 to -5].

Murine and human T11 (CD2) cDNA sequences suggest a common signal transduction mechanism.

The murine equivalent of the cDNA encoding the human T11 (CD2) sheep erythrocyte-binding protein has been cloned. It codes for a putative transmembrane protein which is homologous to human T11. In contrast to immunoglobulins whose domains consist of anti-parallel beta sheets, we predict that mouse and human T11 external domains probably belong to the alpha/beta protein folding class.

Molecular cloning and expression of T11 cDNAs reveal a receptor-like structure on human T lymphocytes.

The T11 (CD2) sheep-erythrocyte-binding protein is a T-cell surface molecule involved in activation of T lymphocytes and thymocytes, including those lacking the T3-Ti antigen-receptor complex. The primary structure of T11 was deduced from protein microsequencing and cDNA cloning. The mature human protein appears to be divided into three domains: a hydrophilic 185 amino acid external domain bearing only limited homology to the T-cell surface protein T4 and the immunoglobulin kappa light chain variable region, a 25 amino acid hydrophobic transmembrane segment, and a 126 amino acid cytoplasmic domain rich in prolines and basic residues.

Leukocytes from four patients with complete or partial Leu-CAM deficiency contain the common beta-subunit precursor and beta-subunit messenger RNA.

Deficiency of a family of three leukocyte adhesion molecules (Leu-CAM) is associated with recurrent and life-threatening bacterial infections in man. Each of the three antigens, Mo1, LFA-1, and Leu M5 has a distinct alpha subunit noncovalently associated with a common beta subunit that appears to be required for the expression of these antigens on the cell surface. To investigate the molecular basis of Leu-CAM deficiency, we studied leukocytes from four unrelated patients suffering from complete or partial Leu-CAM deficiency using immunoprecipitation of metabolically labeled proteins, RNA extraction, and Northern blot analysis.

Hypercholeresis induced by norchenodeoxycholate in biliary fistula rodent.

The biliary recovery and effect on bile flow and biliary bicarbonate secretion of infused norchenodeoxycholate (nor-CDC), the synthetically prepared C23 homologue of chenodeoxycholate (CDC), were defined in the anesthetized biliary fistula hamster, rat, and guinea pig and compared with those of its taurine conjugate as well as those of the natural C24 bile acid, CDC. In the hamster and rat, nor-CDC was recovered slowly in bile in contrast to its taurine conjugate or CDC. Hepatic biotransformation of nor-CDC was complex.

Clonal composition of T cells in lymphomatoid papulosis.

A cDNA of the C beta 2 gene of the T-cell receptor was used as a probe to investigate the clonal composition of T cells in skin lesions of 5 patients with lymphomatoid papulosis (LyP), a chronic recurrent eruption characterized by morphologically abnormal activated T cells in the cutaneous infiltrate. Clonal T-cell populations, as evidenced by rearranged DNA bands, were demonstrated in the skin lesions of four patients, one of whom has shown clinical progression toward lymphoma. Three of these patients had lesions of type A histology, a type previously shown to be associated with aneuploidy.

Amino acid sequence data of alpha-tubulin from myxamoebae of Physarum polycephalum.

About 96% of the amino acid sequence of an alpha-tubulin from the slime mould Physarum polycephalum has been determined. Of 430 sequenced amino acids, 30 differ from the deduced amino acid sequence of a recently published alpha-tubulin complementary DNA from the plasmodial form of P. polycephalum.

Amino-acid sequence data of beta-tubulin from Physarum polycephalum myxamoebae.

Starting with 7.7 mg of a beta-tubulin isolated from myxamoebae of the slime mould Physarum polycephalum, 90% of the sequence has been determined by the Edman degradation of peptides generated by cyanogen bromide, trypsin and Staphylococcus aureus protease. Differences to other beta-tubulins are mainly conservative and spread evenly throughout the chain except for a high concentration at the C-terminus.

Liquid-chromatographic analysis for cyclosporine with use of a microbore column and small sample volume.

This liquid-chromatographic assay requires 0.2 to 0.5 mL of whole blood, avoids the use of diethyl ether, and consumes only 10 to 20% of the solvents used in prior methods.

Determination of chenodiol bioequivalence using an immobilized multi-enzyme bioluminescence technique.

Measurement of the bioequivalence of formulations of chenodiol, a bile acid which is used for gallstone dissolution, is difficult because its high first-pass clearance results in low plasma levels after ingestion of usual dosages. To solve this problem, a new method was developed to determine the bioequivalence of several chenodiol formulations. The method included the following steps: isolation of all bile acids from serum by absorption to a hydrophobic resin, elution of bile acids from the resin by methanol, separation of the unconjugated bile acid fraction by an ion-exchange procedure, and bioluminescence measurement of the unconjugated 7 alpha-hydroxy bile acids using Sepharose beads containing co-immobilized 7 alpha-hydroxysteroid dehydrogenase, diaphorase, and luciferase.