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C L Howe

Publications and source records attributed to C L Howe.

11 recordsLinked to original sources
PubMed1990

Characterization and cloning of lgp110, a lysosomal membrane glycoprotein from mouse and rat cells.

lgp110 is a heavily glycosylated intrinsic protein of lysosomal membranes. Initially defined by monoclonal antibodies against mouse liver lysosomes, it consists of a 45-kilodalton core polypeptide with O-linked and 17 asparagine-linked oligosaccharide side chains in mouse cells. Sialic acid residues make the mature protein extremely acidic, with an isoelectric point of between 2 and 4 in both normal tissues and most cultured cell lines. Partial sequencing of mouse lgp110 allowed oligonucleotide probes to be constructed for the screening of several mouse cDNA libraries. A partial cDNA clone for mouse lgp110 was found and used for additional library screening, generating a cDNA clone covering all of the coding sequence of mature rat lgp110 as well as genomic clones covering most of the mouse gene. These new clones bring to seven the number of lysosomal membrane proteins whose amino acid sequences can be deduced, and two distinct but highly similar groups (designated lgp-A and lgp-B) can now be defined. Sequence comparisons suggest that differences within each group reflect species variations of the same protein and that lgp-A and lgp-B probably diverged from a common ancestor prior to the evolup4f1ary divergence of birds and mammals. Individual cells and individual lysosomes possess both lgp-A and lgp-B, suggesting that these two proteins have different functions. Mouse lgp110 is encoded by at least seven exons; intron positions suggest that the two homologous ectodomains of each lgp arose through gene duplication.

Amino Acid Sequence↗
PubMed1988

Derived protein sequence, oligosaccharides, and membrane insertion of the 120-kDa lysosomal membrane glycoprotein (lgp120): identification of a highly conserved family of lysosomal membrane glycoproteins.

The 120-kDa lysosomal membrane glycoprotein (lgp120) is an acidic, heavily glycosylated membrane protein enriched in the lysosomal membrane. To determine the basis for its selective transport to and stability in lysosomes, we have investigated the structure of lgp120. By using an oligonucleotide probe corresponding to the amino terminus of rat lgp120, we isolated and characterized cDNA clones containing the entire coding region. The deduced amino acid sequence demonstrates that lgp120 contains a putative signal peptide, 18 sites for N-linked glycosylation, a single membrane-spanning segment, and a short (11 amino acid) cytosolic tail. The sequence suggests a distinct domain organization, with two luminal glycosylated regions separated by a nonglycosylated proline-rich region. Proteolysis in detergent showed that the protein was not intrinsically resistant to exogenous or endogenous proteases. The N-linked oligosaccharides on lgp120, tetraantennary structures with two lactosamine repeats on one of the branches, were not different from those of glycoproteins on the plasma membrane. lgp120 was similar in its domain organization and portions of its amino acid sequence to the avian 100-kDa lysosomal membrane protein LEP100 [Fambrough, D. M., Takeyasu, K., Lippincott-Schwartz, J., Siegel, N. R. & Somerville, D. (1988) J. Cell Biol. 106, 61-67], and to a distinct 110-kDa lysosomal membrane protein (lgp110) that colocalizes with lgp120. The similarities between lysosomal membrane glycoproteins from diverse species, coupled with the fact that at least two distinct lysosomal membrane glycoproteins are expressed in a single species, indicate the existence of a conserved family of glycoproteins enriched in the lysosomal membrane.

Amino Acid Sequence↗
PubMed1987

Characterization of intestinal brush border cytoskeletal proteins of normal and neoplastic human epithelial cells. A comparison with the avian brush border.

The elaborate cytoskeletal matrix underlying the intestinal epithelial cell brush border (BB) is the hallmark of a mature enterocyte. As such, alterations in this structure are potentially useful as markers aiding in the recognition of subtle defects in cell maturation, such as those accompanying dysplasia and neoplasia. For exploration of this hypothesis, the BB components of human ileal and colonic enterocytes have been compared structurally and biochemically with the well-characterized avian BB, and alterations in the BB cytoskeleton in various states of dysplasia and neoplasia have been identified. Ultrastructural analysis of isolated human ileal BBs indicate that the human BB is structurally homologous to BBs isolated from chicken and other mammalian sources. Like other mammalian BBs (eg, from rat) the terminal web cytoskeleton of the human BB is less extensive than that in the avian BB. Immunochemical analysis of isolated human BBs indicates that the major proteins of the avian microvillar actin bundle, villin, fimbrin, and the 110-kd subunit of the 110K-calmodulin complex, are all present in the human BB. The terminal web protein myosin is also present. Unlike the terminal web of the avian BB, which contains a BB-specific isoform of spectrin, TW 260/240, the human BB contains the more widely distributed spectrin isoform, fodrin. In addition, the human BB contains multiple proteins immunoreactive with antibodies to protein 4.1, a spectrin/actin binding protein that is absent from the avian BB. Immunolocalization studies examining the distribution of the BB-specific microvillar protein, villin, in human colonic mucosa indicate that the localization of this protein is disrupted in certain dysplastic and neoplastic states. Thus, both the expression and/or distribution of BB-specific proteins such as villin may be useful markers for defects in the differentiation state of the enterocyte.

Animals↗
PubMed1986

Developmental theory and adolescent sexual behavior.

Although substantial research exists regarding adolescent sexual behavior, there is no unifying framework. In this article, a developmental framework is applied to the subject of adolescent sexual behavior.

Adolescent↗
PubMed1985

Mechanisms of cytoskeletal regulation: modulation of membrane affinity in avian brush border and erythrocyte spectrins.

The spectrins isolated from chicken erythrocytes and chicken intestinal brush border, TW260/240, share a common alpha subunit and a tissue-specific beta subunit. The ability of these related proteins to bind human erythrocyte inside out vesicles (IOVs) and human erythrocyte ankyrin in vitro have been quantitatively compared with human erythrocyte spectrin. Chicken erythrocyte spectrin binds human IOVs and human ankyrin with affinities nearly identical to that for human erythrocyte spectrin. TW260/240 does not significantly bind to either IOVs or ankyrin. These results demonstrate a remarkable tissue preservation of ankyrin-binding capacity, even between diverse species, and confirm the role of the avian beta-spectrins in modulating this functionality. Avian brush border spectrin may represent a unique spectrin which serves primarily as a filament cross-linker and which does not interact strongly with membrane-associated proteins.

Animals↗
PubMed1979

Toxoplasma gondii-vertebrate cell interactions. II. The intracellular reproductive phase.

The reproduction of Toxoplasma gondii RH-strain in vertebrate cells was studied in a controlled-environment culture system. The lag period before reproduction and the doubling time of individual parasites were determined using a least-squares linear regression method of analysis which does not artificially constrain the data. In the majority of cases, the time intercept of the linear regression line was either zero, implying the lack of a lag phase before reproduction, or negative, implying the parasite had completed part of its reproductive cycle before entering the host cell. The mean doubling time of T. gondii is 10.9 h in bovine embryo skeletal muscle cells and 8.3 h in HeLa cells. This difference is not significant at the 5% level. The population doubling times of mouse-derived parasites is best described by a gamma distribution.

Animals↗
PubMed1977

Toxoplasma gondii-vertebrate cell interactions. I. The influence of bicarbonate ion, CO2, pH and host cell culture age on the invasion of vertebrate cells in vitro.

A controlled-environment culture system was used to show that both physical and biologic parameters can influence the penetration of vertebrate cells by Toxoplasma gondii. The optimum bicarbonate ion concentration for the penetration of bovine embryo skeletal muscle (BESM) cells is 36.25 mM. Higher or lower bicarbonate ion concentrations are increasingly inhibitory to penetration. As CO2 increases in the range from 0.5-3.7 mM, penetration is progressively inhibited. No relationship was found between penetration and pH in the pH range of 6.949-7.765. The culture age of the BESM cells directly influenced the ability of the parasites to penetrate the cells. Older BESM cells were more refractory to penetration than younger cells.

Animals↗
PubMed1977

The effects of Lampit (Bayer 2502) on the interaction of Trypanosoma cruzi with vertebrate cells in vitro.

The effects of 3-methyl-4-(5'-nitrofurfurylidene-amino)-tetrahydro-4H-1,4-thiazine-1,1-dioxide [Lampit, Bayer 2502] on the intracellular cycle of Trypanosoma cruzi were studied with an in vitro steady-state culture system that permitted the continuous analysis of individual host cell-parasite interactions. Lampit concentrations of 10(-4) and 10(-5) M significantly affected the ability of trypomastigotes to penetrate vertebrate cells. Lampit concentrations above 10(-4) M were toxic to the host cell population and Lampit concentrations below 10(-5) M did not affect the ability of trypomastigotes to penetrate vertebrate cells. Lampit concentrations of 10(-5) M or greater completely inhibited the intracellular cycle of T. cruzi whereas Lampit concentrations of 10(-7) M or less had no effect on the intracellular cycle. Continuous perfusion with 10(-6) M Lampit resulted in a linear increase in intracellular parasite reproduction time. A stable strain of T. cruzi was produced in vitro that was resistant to a 100-fold greater concentration of Lampit that the parent strain.

Animals↗
PubMed1976

The attraction of Trypanosoma cruzi to vertebrate cells in vitro.

A video technic is described that permits a quantification of the degree of attraction of Trypanosoma cruzi trypomastigotes to vertebrate cells in vitro. Bovine embryo skeletal muscle cells (BESM), HeLa cells and Vero cells all attract a myotropic strain of T. cruzi trypomastigotes. BESM cells, however, are 2-fold more attractive to trypomastigotes than HeLa cells and 10-fold more attractive than Vero cells. Heat-inactivation of BESM cells abolishes their ability to respire and also to attract T. cruzi trypomastigotes. As there is no difference in the endogenous oxygen consumption between BESM, HeLa, and Vero cells, it is unlikely that differences in the attraction of trypomastigotes to the 3 cell types are due to variations in the magnitude of pO2 or pCO2 gradients in the milieu around the cells.

Animals↗