PMID: 9555946Apr 29, 1998Paper

The carboxy-terminal region of human lipoprotein lipase is necessary for its exit from the endoplasmic reticulum.

Journal of Lipid Research
R BuscàS Vilaró

Abstract

Certain missense substitutions on the human lipase (hLPL) gene produce mutated proteins that are retained in different compartments along the secretory pathway. The purpose of the present study was to elucidate whether the C-terminal domain of the hLPL molecule could be important for secretion. We constructed by site-directed mutagenesis three carboxy-terminal mutated (F388-->Stop, K428-->Stop and K441-->Stop) hLPL cDNAs that were expressed in COS1 cells. Immunoblotting of cell extracts showed that all three constructs led to similar levels of protein. Both wild type (WT) hLPL and the truncated K441-->Stop hLPL were secreted to the extracellular medium, and presented a similar intracellular distribution pattern as shown by immunofluorescence. Neither F388-->Stop nor K428-->Stop hLPL protein was detected in cell medium. Immunofluorescence experiments showed that both truncated hLPL were retained within an intracellular compartment, which became larger. Double immunofluorescence analysis using antibodies against LPL and antiprotein disulfide isomerase as a marker showed that the truncated K428-->Stop hLPL was retained within the rough endoplasmic reticulum. This truncated protein was not found in other compartments in the secreto...Continue Reading

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