Functional importance of apolipoprotein A5 185G in the activation of lipoprotein lipase.
BACKGROUND
Apolipoprotein A5 (APOA5) over-expression enhances lipolysis of triglyceride (TG) through stimulation of lipoprotein lipase (LPL) activity; however, an APOA5 G185C variant was found associated with hypertriglyceridemia. The aim of this study was, therefore, to explore the importance of APOA5 185GG in the activation of LPL.


METHODS
A fragment containing mature human APOA5 cDNA was obtained by RT-PCR and subcloned into pET-15b vector. Site-directed mutagenesis was performed to generate 19 variants. Recombinant human APOA5 wild type and variants were produced in Escherichia coli, and then activation of LPL was measured.


RESULTS
Activity of APOA5 variants on LPL-mediated 1,2-dimyristoyl-sn-glycero-3-phosphocholine hydrolysis was reduced by 17 to 74% in comparison to wild type APOA5 (P<0.0001). All variants also showed reduced activation (P<0.0001) of LPL-mediated hydrolysis of very low-density lipoprotein (VLDL); activation abilities of APOA5 variants ranged from 31 to 81% of wild-type APOA5.


CONCLUSIONS
APOA5 residue 185G is very important in LPL-mediated VLDL hydrolysis, and any mutation at this residue will decrease LPL activation and concomitant TG modulation.
Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taiwan.
Yi-Jan
YJ
Huang
Yen-Lin
YL
Lin
Chi-I
CI
Chiang
Ching-Tzu
CT
Yen
Shu-Wha
SW
Lin
Jau-Tsuen
JT
Kao
D000072040:Apolipoprotein A-V; D001054:Apolipoproteins A / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers; D018076:DNA, Complementary; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008071:Lipoprotein Lipase / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D059748:Proteolysis; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
C437704:APOA5 protein, human; D000072040:Apolipoprotein A-V; D001054:Apolipoproteins A; D017931:DNA Primers; D018076:DNA, Complementary; D011994:Recombinant Proteins; D008071:Lipoprotein Lipase