LC3, a microtubule-associated protein1A/B light chain3, is involved in cytoplasmic lipid droplet formation.
The cytoplasmic lipid droplet (LD) is one of organelles that has a neutral lipid core with a single phospholipid layer. LDs are believed to be generated between the two leaflets of the endoplasmic reticulum (ER) membrane and to play various roles, such as high effective energy storage. However, it remains largely unknown how LDs are generated and grow in the cytoplasm. We have previously shown that the Atg conjugation system that is essential for autophagosome formation is involved in LD formation in hepatocytes and cardiac myocytes. We show here that LC3 itself is involved in LD formation by using RNA interference (RNAi). All cultured cell lines examined, in which the expression of LC3 was suppressed by RNAi, showed reduced LD formation. Triacylglycerol, a major component of LDs, was synthesized and degraded in LC3 mRNA-knockdown cells as well as in control cells. Interestingly, potential of the bulk protein degradation in the knockdown-cells was also evident in the control cells. These findings indicate that LC3 is involved in the LD formation regardless of the bulk degradation, and that LC3 has two pivotal roles in cellular homeostasis mediated by autophagy and lipid metabolism.
Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Sciences, Japan.
Masahiro
M
Shibata
Kentaro
K
Yoshimura
Hirosumi
H
Tamura
Takashi
T
Ueno
Taki
T
Nishimura
Takao
T
Inoue
Mitsuho
M
Sasaki
Masato
M
Koike
Hiroyuki
H
Arai
Eiki
E
Kominami
Yasuo
Y
Uchiyama
D000818:Animals; D001343:Autophagy; D003593:Cytoplasm / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D050356:Lipid Metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D016716:PC12 Cells; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D014280:Triglycerides / Q000378:metabolism
D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D014280:Triglycerides; C526109:Anxa3 protein, rat