Surface membrane glycoproteins of wild-type and differentiation-inducer- resistant HL-60 cells

Abstract Surface membrane glycoproteins (SMGs) of cells from the parental wild- type HL-60 cell line and from three sublines variably cross-resistant to the granulocyte differentiation-inducing effects of retinoic acid (RA), dimethylsulfoxide (DMSO), and certain purine bases (6-thioguanine [6TG] or hypoxanthine) were studied by one-dimensional and two- dimensional gel electrophoresis. After both oligosaccharide (periodate/borotritide) and peptide (1,3,4,6-tetrachloro-3 alpha, 6 alpha-diphenylglycouril) ectolabeling procedures, striking common changes were noted in the gel electrophoretic patterns of the SMGs from the RA- and 6TG-resistant sublines compared to those from the wild-type HL-60 line or the DMSO-resistant subline. Most prominently, this included the presence in the RA- and 6TG-resistant cells of an apparent high molecular weight acidic glycoprotein(s) (mol wt, 200 to 285 kilodaltons [kD]; isoelectric point range [pl], 4.5 to 6.0) not observed in the wild-type or DMSO-resistant cells and, conversely, the presence of a lower molecular weight glycoprotein(s) (mol wt, 120 to 165 kD; pl, 4.2 to 5.9) in the wild-type and DMSO-resistant cells, which was absent or much reduced in the RA- and 6TG-resistant cells. These acidic SMGs did not change as a function of the induction of granulocyte differentiation. However, some other more basic SMGs varied as a function of granulocyte differentiation in both the wild-type and differentiation inducer-resistant sublines, including the loss of the transferrin receptor and the gain of a mol wt 55- to 60-kD neutrophil- associated protein. In the context of previously reported information, these results indicate (1) that the overall pattern of SMG changes in the RA- and 6TG-resistant cells closely resembles that associated with multidrug (pleiotropic) resistance to cytotoxic agents in a variety of mammalian cells; (2) that the RA/6TG resistance-associated SMG changes are not granulocyte differentiation stage-specific; and (3) that either the RA/6TG resistance-associated SMG changes are not related to the resistance mechanism or they are involved in the resistance/cross- resistance mechanism(s) for RA/purine bases but not for DMSO.</jats:p

Surface membrane glycoproteins of wild-type and differentiation-inducer- resistant HL-60 cells

Surface membrane glycoproteins (SMGs) of cells from the parental wild- type HL-60 cell line and from three sublines variably cross-resistant to the granulocyte differentiation-inducing effects of retinoic acid (RA), dimethylsulfoxide (DMSO), and certain purine bases (6-thioguanine [6TG] or hypoxanthine) were studied by one-dimensional and two- dimensional gel electrophoresis. After both oligosaccharide (periodate/borotritide) and peptide (1,3,4,6-tetrachloro-3 alpha, 6 alpha-diphenylglycouril) ectolabeling procedures, striking common changes were noted in the gel electrophoretic patterns of the SMGs from the RA- and 6TG-resistant sublines compared to those from the wild-type HL-60 line or the DMSO-resistant subline. Most prominently, this included the presence in the RA- and 6TG-resistant cells of an apparent high molecular weight acidic glycoprotein(s) (mol wt, 200 to 285 kilodaltons [kD]; isoelectric point range [pl], 4.5 to 6.0) not observed in the wild-type or DMSO-resistant cells and, conversely, the presence of a lower molecular weight glycoprotein(s) (mol wt, 120 to 165 kD; pl, 4.2 to 5.9) in the wild-type and DMSO-resistant cells, which was absent or much reduced in the RA- and 6TG-resistant cells. These acidic SMGs did not change as a function of the induction of granulocyte differentiation. However, some other more basic SMGs varied as a function of granulocyte differentiation in both the wild-type and differentiation inducer-resistant sublines, including the loss of the transferrin receptor and the gain of a mol wt 55- to 60-kD neutrophil- associated protein. In the context of previously reported information, these results indicate (1) that the overall pattern of SMG changes in the RA- and 6TG-resistant cells closely resembles that associated with multidrug (pleiotropic) resistance to cytotoxic agents in a variety of mammalian cells; (2) that the RA/6TG resistance-associated SMG changes are not granulocyte differentiation stage-specific; and (3) that either the RA/6TG resistance-associated SMG changes are not related to the resistance mechanism or they are involved in the resistance/cross- resistance mechanism(s) for RA/purine bases but not for DMSO.</jats:p

Hyposialylation of differentiation-inducer-resistant HL-60 cells

Abstract The total sialic acid concent of retinoic acid (RA)-resistant or 6- thioguanine (6TG)-resistant HL-60 cells was more than tenfold lower and of dimethylsulfoxide (DMSO)-resistant HL-60 cells was approximately twofold lower than that of parental, wild-type (wt) HL-60 cells. Neuraminidase-inaccessible, ie residual cell-associated sialic acid after neuraminidase treatment, was four- to twelvefold lower in the three differentiation-inducer-resistant sublines than in the parent line. Neuraminidase treatment of 125I-labeled surface membrane glycoproteins (SMGs) from wt HL-60 cells converted the two-dimensional gel electrophoretic pattern to one having features in common with RA- and 6TG-resistant cells. However, neuraminidase treatment did not alter the sensitivity of wt HL-60 cells to differentiation induction by RA, hypoxanthine (purine base), or DMSO. These results indicate that differences in peripheral, neuraminidase-accessible sialic acids are important determinants of the gel electrophoretic mobility of the SMGs of the HL-60 line and sublines but are not likely related to the differentiation-resistance mechanism. Further studies are required to determine if hyposialylation of cryptic, neuraminidase-inaccessible sites has functional significance.</jats:p

Hyposialylation of differentiation-inducer-resistant HL-60 cells

The total sialic acid concent of retinoic acid (RA)-resistant or 6- thioguanine (6TG)-resistant HL-60 cells was more than tenfold lower and of dimethylsulfoxide (DMSO)-resistant HL-60 cells was approximately twofold lower than that of parental, wild-type (wt) HL-60 cells. Neuraminidase-inaccessible, ie residual cell-associated sialic acid after neuraminidase treatment, was four- to twelvefold lower in the three differentiation-inducer-resistant sublines than in the parent line. Neuraminidase treatment of 125I-labeled surface membrane glycoproteins (SMGs) from wt HL-60 cells converted the two-dimensional gel electrophoretic pattern to one having features in common with RA- and 6TG-resistant cells. However, neuraminidase treatment did not alter the sensitivity of wt HL-60 cells to differentiation induction by RA, hypoxanthine (purine base), or DMSO. These results indicate that differences in peripheral, neuraminidase-accessible sialic acids are important determinants of the gel electrophoretic mobility of the SMGs of the HL-60 line and sublines but are not likely related to the differentiation-resistance mechanism. Further studies are required to determine if hyposialylation of cryptic, neuraminidase-inaccessible sites has functional significance.</jats:p

Evolutionary and structural analyses uncover a role for solvent interactions in the diversification of cocoonases in butterflies

Multi-omic approaches promise to supply the power to detect genes underlying disease and fitness-related phenotypes. Optimal use of the resulting profusion of data requires detailed investigation of individual candidate genes, a challenging proposition. Here, we combine transcriptomic and genomic data with molecular modelling of candidate enzymes to characterize the evolutionary history and function of the serine protease cocoonase. Heliconius butterflies possess the unique ability to feed on pollen; recent work has identified cocoonase as a candidate gene in pollen digestion. Cocoonase was first described in moths, where it aids in eclosure from the cocoon and is present as a single copy gene. In heliconiine butterflies it is duplicated and highly expressed in the mouthparts of adults. At least six copies of cocoonase are present in Heliconius melpomene and copy number varies across H. melpomene sub-populations. Most cocoonase genes are under purifying selection, however branch-site analyses suggest cocoonase 3 genes may have evolved under episodic diversifying selection. Molecular modelling of cocoonase proteins and examination of their predicted structures revealed that the active site region of each type has a similar structure to trypsin, with the same predicted substrate specificity across types. Variation among heliconiine cocoonases instead lies in the outward-facing residues involved in solvent interaction. Thus, the neofunctionalization of cocoonase duplicates appears to have resulted from the need for these serine proteases to operate in diverse biochemical environments. We suggest that cocoonase may have played a buffering role in feeding during the diversification of Heliconius across the neotropics by enabling these butterflies to digest protein from a range of biochemical milieux