Journal
JOURNAL OF LIPID RESEARCH
Volume 44, Issue 3, Pages 539-546Publisher
ELSEVIER
DOI: 10.1194/jlr.M200420-JLR200
Keywords
apoA-I proteolysis; mast cell chymase; reconstituted HDL
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Mast cell chymase, a chymotrypsin-like neutral protease, can proteolyze HDL3. Here we studied the ability of rat and human chymase to proteolyze discoidal prebeta-migrating reconstituted HDL particles (rHDLs) containing either apolipoprotein A-I (apoA-I) or apoA-II. Both chymases cleaved apoA-I in rHDL at identical sites, either at the N-terminus (Tyr(18) or Phe(33)) or at the C-terminus (Phe(225)), so generating three major truncated polypeptides that remained bound to the rHDL. The cleavage sites were independent of the size of the rHDL particles, but small particles were more susceptible to degradation than bigger ones. Chymase-induced truncation of apoA-I yielded functionally compromised rHDL with reduced ability to promote cellular cholesterol efflux. In sharp contrast to apoA-I, apoA-II was resistant to degradation. However, when apoA-II was present in rHDL that also contained apoA-I, it was degraded by chymase.jlr We conclude that chymase reduces the ability of apoA-I in discoidal rHDL particles to induce cholesterol efflux by cleaving off either its amino- or carboxy-terminal portion. This observation supports the concept that limited extracellular proteolysis of apoA-I is one pathophysiologic mechanism leading to the generation and maintenance of foam cells in atherosclerotic lesions.
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