The lack of the C-terminal domain of adipose triglyceride lipase causes neutral lipid storage disease through impaired interactions with lipid droplets.
BACKGROUND
The molecular mechanisms by which triglycerides in lipid droplets (LDs) are synthesized, stored, and degraded need to be elucidated.


OBJECTIVE
The objectives were to report siblings with neutral lipid storage disease with myopathy (NLSDM) with a novel mutation of adipose triglyceride lipase (ATGL) and determine whether the C-terminal part of ATGL containing the hydrophobic region plays a role in the interaction with LDs.


METHODS
Skin fibroblasts and peripheral blood leukocytes were obtained from NLSDM patients. In vitro experiments were performed with fibroblasts and COS7 cells.


METHODS
Transfection studies were used to assess the effects of various recombinant ATGL proteins on lipase activities and lipid contents. Fluorescence microscopy were used for determination of intracellular distribution of ATGL proteins.


RESULTS
The direct sequence of ATGL cDNA reveals that a patient is a homozygote for the 4-bp deletion, leading to a premature stop codon and causes the lack of the C terminus of the protein including the hydrophobic domain. Overexpressed control ATGL in NLSDM fibroblasts was found around the rims of LDs and caused significantly reduced cellular lipid accumulation. In contrast, NLSDM ATGL was homogeneously located in the cytoplasm despite the presence of LDs and had almost no effect on LD degradation despite its similar lipase activity. A series of C-terminal truncated ATGLs without the intact hydrophobic domain failed to localize around and degrade LDs.


CONCLUSIONS
These findings indicate that the domain including the hydrophobic region of ATGL was essential for association with LDs.
Kobayashi
Kunihisa
K
Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Japan. nihisak@med.kyushu-u.ac.jp
Inoguchi
Toyoshi
T
Maeda
Yasutaka
Y
Nakashima
Naoki
N
Kuwano
Asako
A
Eto
Erina
E
Ueno
Noriko
N
Sasaki
Shuji
S
Sawada
Fumi
F
Fujii
Masakazu
M
Matoba
Yuka
Y
Sumiyoshi
Shinji
S
Kawate
Hisaya
H
Takayanagi
Ryoichi
R
D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008049:Lipase / Q000737:chemistry / Q000235:genetics*; D050356:Lipid Metabolism; D052439:Lipid Metabolism Disorders / Q000235:genetics*; D008875:Middle Aged; D009135:Muscular Diseases / Q000235:genetics*; D009154:Mutation; D017434:Protein Structure, Tertiary; D014280:Triglycerides / Q000378:metabolism*; D000217:Acyltransferases
D008049:Lipase; D014280:Triglycerides; C494794:PNPLA2 protein, human; D000217:Acyltransferases