Abstract 19748: Mature Enterocytes Lose Their Ability to Secrete Pcsk9
Introduction: Proprotein Convertase Subtilisin Kexin of type 9 (PCSK9) promotes LDL receptor lysosomal degradation and is a key regulator of cholesterol metabolism. Beyond the liver, the small intestine is the second organ where PCSK9 is highly expressed, but its ability to secrete PCSK9 remains a matter of debate.
Hypothesis: Our study aims to determine whether the small intestine and enterocytes are able to secrete PCSK9.
Methods: In vivo, intestinal PCSK9 secretion was assessed by ELISA and western blot in wild-type (WT) and liver-specific PCSK9-deficient mice (L-PCSK9 KO). Ex vivo, local PCSK9 secretion was evaluated from human and murine intestinal explants mounted in Ussing chambers. In vitro, PCSK9 secretion was measured from human intestinal Caco-2 cells along their differentiation.
Results: In vivo, PCSK9 concentrations were similar in tail and portal blood and mesenteric lymph from WT mice and undetectable in the portal blood from L-PCSK9 KO mice. Similarly, no local human and murine PCSK9 secretion was measured in Ussing Chambers. Interestingly, PCSK9 secretion was detected at significant level during the first 10 days of Caco-2 cells differentiation then dropped by more than 30 times to become null after 16 days. Despite no change in PCSK9 mRNA levels, intracellular PCSK9 protein content was reduced by 4 times between day 8 and 16 and was associated with a PCSK9 half-life reduction. While the cleavage and PCSK9 trafficking from ER to Golgi were not altered with differentiation, mature PCSK9 accumulated in the Golgi. 2D electrophoresis revealed that the PCSK9 isoelectric point was reduced at late stages of differentiation, suggesting a potential change in the PCSK9 phosphorylation status.
Conclusions: We show that mature enterocyte lose their ability to secrete PCSK9. Underlying molecular mechanisms remain under investigation but involve at least a PCSK9 half-life decrease and a post-traductional modification altering the post-golgi trafficking of PCSK9.
Author Disclosures: F. Moreau: None. D. Garcon: None. C. Blanchard: None. A. Ayer: None. X. Prieur: None. M. Neunlist: None. A. Prat: None. N. Seidah: None. B. Cariou: None. C. Le May: None.
- © 2016 by American Heart Association, Inc.