Biomedical subjects

L Wikström

Publications and source records attributed to L Wikström.

11 recordsLinked to original sources

PubMed1995

Liver transplantation in familial amyloidotic polyneuropathy. Follow-up of the first 20 Swedish patients.

Familial amyloidotic polyneuropathy (FAP) is an inherited fatal form of amyloidosis caused by mutant transthyretin. The disease is characterized by progressive peripheral and autonomic neuropathy. Most of the transthyretin is produced by the liver, and we have shown previously that the metabolic deficiency can be corrected by liver transplantation. In the present study, the clinical results from the first 20 patients who underwent liver transplantation for FAP in Sweden are evaluated. Three of the patients suffered from renal failure and underwent a simultaneous kidney transplantation. Fourteen of the 20 patients (70%) are alive 10-52 months after transplantation. The patients' nutritional status at the time of transplantation had a significant impact on mortality and morbidity (P < 0.007). Long-standing disease was another negative prognostic factor (P < 0.02). One year after transplantation, the nutritional status had improved (P < 0.02). Improvements were also noted in walking capacity and for gastrointestinal and urogenital symptoms. The results show that liver transplantation offers an effective means to treat patients with FAP. The procedure should preferably be performed before the nutritional status is poor and advanced organ dysfunction has developed.

Adult↗

PubMed1992

Calcium is required for folding of newly made subunits of the asialoglycoprotein receptor within the endoplasmic reticulum.

By resolving immunoprecipitates on nonreducing sodium dodecyl sulfate gels, we have detected several disulfide-bonded intermediates in folding within the endoplasmic reticulum of newly made H1 subunits of the asialoglycoprotein receptor. H1 in the endoplasmic reticulum (ER) can be partially unfolded by treatment of cells with dithiothreitol, but H1 in Golgi or post-Golgi organelles is resistant to such unfolding. This defines a late step in H1 folding that occurs just prior to exit from the ER. Depletion of calcium from the endoplasmic reticulum, either by treatment with A23187 or thapsigargin, has no effect on folding or secretion of newly made albumin, but totally blocks H1 maturation from the ER. No ER intermediates in H1 folding are formed in cells treated with A23187 or thapsigargin, indicating that at least an early step in H1 folding requires a high Ca2+ concentration in the ER lumen. As judged by cross-linking experiments, formation of H1 dimers and trimers occurs immediately after biosynthesis of the peptide chain, before monomer folding, and occurs normally in cells in which ER Ca2+ is reduced and where the monomer never folds properly. Calcium is essential for the asialoglycoprotein receptor to bind galactose, and our results suggest that Ca2+ is also essential for the receptor polypeptides to fold in the ER.

Albumins↗

PubMed1992

Endoplasmic reticulum degradation of a subunit of the asialoglycoprotein receptor in vitro. Vesicular transport from endoplasmic reticulum is unnecessary.

The H2a subunit of the human asialoglycoprotein receptor is rapidly degraded from the endoplasmic reticulum (ER) when expressed in CHO15B cells. We have reconstituted ER degradation of H2a in semipermeable cells. At least the initial step in degradation (a proteolytic cleavage inhibited by N alpha-p-tosyl-L-lysine chloromethyl ketone and L-1-tosylamido-2-phenylethyl chloromethyl ketone) can occur in vitro in the presence of guanosine 5'-3-O-(thio)triphosphate or in the absence of ATP and postnuclear supernatant, conditions that do not allow vesicular transport of subunit H1 from the ER to the Golgi. We conclude that vesicular transport from the ER is not required for ER degradation of H2a to occur and thus that it takes place in the ER itself.

Asialoglycoprotein Receptor↗

PubMed1991

Nonlysosomal, pre-Golgi degradation of unassembled asialoglycoprotein receptor subunits: a TLCK- and TPCK-sensitive cleavage within the ER.

The human asialoglycoprotein receptor subunit H2a is cotranslationally inserted into the ER membrane. When expressed together with subunit H1 in mouse fibroblasts part forms a hetero-oligomer that is transported to the cell surface, but when expressed alone it is all rapidly degraded. Degradation is insensitive to lysosomotropic agents and the undegraded precursor is last detected in the ER region of the cell. Small amounts of an intermediate 35-kD degradation product can be detected (Amara, J. F., G. Lederkremer, and H. F. Lodish. 1989. J. Cell Biol. 109:3315). We show here that the oligosaccharides on both precursor H2a and the 35-kD fragment are Man6-9GlcNAc2, structures typically found in pre-Golgi compartments. Subcellular fractionation shows that the intermediate degradation product does not cofractionate with the lysosomal enzyme beta-galactosidase, but is found in a part of the ER that contains ribosomes. Thus the intermediate degradation product is localized in the ER, indicating that the initial degradation event does take place in the ER. All degradation of H2a, including the initial endoproteolytic cleavage generating the 35-kD intermediate, is blocked by the protease inhibitors N-tosyl-L-lysine chloromethyl ketone and N-tosyl-L-phenylalanine chloromethyl ketone. These drugs do not inhibit ER-to-Golgi transport of H1. Depleting the cells of ATP or inhibiting protein synthesis allows the initial endoproteolytic cleavage to occur, but blocks further degradation of the 35-kD intermediate; thus we can convert all cellular H2 into the 35-kD intermediate. Approximately 50% of H2b, a splicing variant differing from H2a by a five amino acid deletion, can be transported to the cell surface, and the rest appears to be degraded by the same pathway as H2a, both when expressed alone in fibroblasts and together with H1 in HepG2 cells. Addition of N-tosyl-L-lysine chloromethyl ketone or N-tosyl-L-phenylalanine chloromethyl ketone blocks degradation of the approximately 50% that is not transported, but does not affect the fraction of H2b that moves to the Golgi region. Thus, a protein destined for degradation will not be transported to the Golgi region if degradation is inhibited.

2,4-Dinitrophenol↗

PubMed1988

Concanavalin A-induced redistribution of surface receptors in Acanthamoeba castellanii at different growth phases.

Concanavalin A (ConA)-induced redistribution of surface receptors has been studied in Acanthamoeba castellanii at different growth phases utilizing double fluorescent techniques and transmission electron microscopy. When the amoebae were incubated with 2 micrograms and 10 micrograms tetramethylrhodamine isothiocyanate (TRITC)-ConA/ml for 4 min and 15 min at 28 degrees C the staining pattern was characterized by various numbers of scattered aggregates of fluorescent ConA. Double labeling of the amoebae showed that the fluorescent aggregates represented internalized label, and the internalization was not preceded by any aggregation of ConA receptors on the cell surface as visualized by incubating with anti-ConA serum followed by fluorescein isothiocyanate-conjugated anti-IgG. Following exposure of the amoebae to 10 micrograms TRITC-ConA/ml for 4 min and 15 min at 28 degrees C intracellular accumulation of some of the fluorescent aggregates in cap-like structures occurred at the logarithmic and postlogarithmic growth phases but not at the early stationary growth phase. Electron microscopic observation of amoebae labeled with ferritin-conjugated ConA at 28 degrees C revealed a uniform surface labeling and an intracellular accumulation of the label in vesicular and tubular structures, and occasionally in cap-like structures. Surface capping of ConA receptors in Acanthamoeba was induced by treating the amoebae with ConA and anti-ConA serum at 0 degrees C followed by incubation at 28 degrees C. The formation of surface caps in Acanthamoeba showed growth-phase dependency, too. The visualization of the surface caps at the electron microscopic level was performed by indirect staining utilizing protein A-colloidal gold.(ABSTRACT TRUNCATED AT 250 WORDS)

Acanthamoeba↗

PubMed1978