Interaction of reconstituted high density lipoprotein discs containing human apolipoprotein A-I (ApoA-I) variants with murine adipocytes and macrophages. Evidence for reduced cholesterol efflux promotion by apoA-I(Pro165-->Arg)
Interaction of cells with both native and reconstituted high density lipoproteins (rHDL) containing apolipoprotein (apo) A-I mediates efflux of cellular cholesterol. To characterize structural requirements for this activity in apoA-I, six different genetic apoA-I variants and the corresponding norma...
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Veröffentlicht in: | The Journal of biological chemistry 1993-02, Vol.268 (4), p.2616-2622 |
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Zusammenfassung: | Interaction of cells with both native and reconstituted high density lipoproteins (rHDL) containing apolipoprotein (apo) A-I
mediates efflux of cellular cholesterol. To characterize structural requirements for this activity in apoA-I, six different
genetic apoA-I variants and the corresponding normal allele products were isolated from heterozygous carriers, reconstituted
with dimyristoylphosphatidylcholine (DMPC) into discoidal HDL and compared with regard to their ability to release intracellular
cholesterol from murine adipocytes and peritoneal macrophages. In previous studies we determined the amino acid changes of
these variants: Pro3-->Arg, Pro4-->Arg, Lys107-->0, Lys107-->Met, Pro165-->Arg, and Glu198-->Lys (von Eckardstein, A., Funke,
H., Walter, M., Altland, K., Benninghoven, A., and Assmann, G. (1990) J. Biol. Chem. 265, 8610-8617) and demonstrated that
all apoA-I variants except apoA-I(Lys107-->0) form discoidal HDL particles with phosphatidylcholine analogues indistinguishable
from normal apoA-I (Jonas, A., von Eckardstein, A., Kezdy, K. E., Steinmetz, A., and Assmann, G. (1991) J. Lipid Res. 32,
95-106). In the present study, all apoA-I.DMPC complexes except those containing apoA-I(Pro165-->Arg) promoted cholesterol
efflux as effectively as those containing normal apoA-I. Cholesterol efflux from adipocytes obtained after 180 min of incubation
with apoA-I(Pro165-->Arg).DMPC complexes was decreased by 30% although this variant was bound to adipocytes with normal affinity.
By contrast, apoA-I(Lys107-->Met).DMPC complexes were decreased in their binding affinity compared to normal apoA-I.DMPC complexes
but normally promoted cholesterol efflux. Incubation of mouse peritoneal macrophages with apoA-I(Pro165-->Arg).DMPC complexes
did also result in a 30% decreased efflux of radiolabeled cholesterol if compared to rHDL with the normal allele product from
the same donor. Together the observations suggest that the substitution of proline at residue 165 interferes with the formation
of a structural domain in apoA-I that is crucial for cellular cholesterol efflux stimulation. Furthermore, our results suggest
that binding of HDL to adipocytes and cholesterol efflux promotion by HDL requires different structural domains. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/S0021-9258(18)53819-9 |