HDL Stimulates apoM Secretion
Apolipoprotein M (apoM) in human plasma is mainly associated with HDL. A retained signal peptide anchors apoM to the lipoproteins. To investigate the role of the signal peptide in the transfer of apoM from the synthesizing cell to the lipoproteins, wildtype apoM cDNA and the Q22A mutant, introducing a signal peptidase cleavage site, were used to stably transfect HEK293 cells, which intrinsically do not express apolipoproteins. When cultured under serum-free conditions, wildtype apoM was, in contrast to Q22A, poorly secreted. Addition of serum or purified HDL stimulated secretion of wildtype apoM, which was recovered in the medium incorporated in HDL. The liver cell line HepG2, which synthesizes HDL, was cultured under serum-free conditions and found to secrete apoM as part of an HDL-like particle. In conclusion, due to its retained signal peptide, apoM is poorly secreted unless HDL is either coexpressed or added to the culture medium.
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Document Type: Research Article
Publication date: 2010-10-01
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- Protein & Peptide Letters publishes short papers in all important aspects of protein and peptide research, including structural studies, recombinant expression, function, synthesis, enzymology, immunology, molecular modeling, drug design etc. Manuscripts must have a significant element of novelty, timeliness and urgency that merit rapid publication. Reports of crystallisation, and preliminary structure determinations of biologically important proteins are acceptable. Purely theoretical papers are also acceptable provided they provide new insight into the principles of protein/peptide structure and function.