Mutation for nonsyndromic mental retardation in the trans-2-enoyl-CoA reductase TER gene involved in fatty acid elongation impairs the enzyme activity and stability, leading to change in sphingolipid profile.
Very long-chain fatty acids (VLCFAs, chain length >C20) exist in tissues throughout the body and are synthesized by repetition of the fatty acid (FA) elongation cycle composed of four successive enzymatic reactions. In mammals, the TER gene is the only gene encoding trans-2-enoyl-CoA reductase, which catalyzes the fourth reaction in the FA elongation cycle. The TER P182L mutation is the pathogenic mutation for nonsyndromic mental retardation. This mutation substitutes a leucine for a proline residue at amino acid 182 in the TER enzyme. Currently, the mechanism by which the TER P182L mutation causes nonsyndromic mental retardation is unknown. To understand the effect of this mutation on the TER enzyme and VLCFA synthesis, we have biochemically characterized the TER P182L mutant enzyme using yeast and mammalian cells transfected with the TER P182L mutant gene and analyzed the FA elongation cycle in the B-lymphoblastoid cell line with the homozygous TER P182L mutation (TER(P182L/P182L) B-lymphoblastoid cell line). We have found that TER P182L mutant enzyme exhibits reduced trans-2-enoyl-CoA reductase activity and protein stability, thereby impairing VLCFA synthesis and, in turn, altering the sphingolipid profile (i.e. decreased level of C24 sphingomyelin and C24 ceramide) in the TER(P182L/P182L) B-lymphoblastoid cell line. We have also found that in addition to the TER enzyme-catalyzed fourth reaction, the third reaction in the FA elongation cycle is affected by the TER P182L mutation. These findings provide new insight into the biochemical defects associated with this genetic mutation.
From the Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12-jo, Nishi 6-chome, Kita-ku, Sapporo 060-0812, Japan.
Kensuke
K
Abe
Yusuke
Y
Ohno
Takayuki
T
Sassa
Ryo
R
Taguchi
Minal
M
Çalışkan
Carole
C
Ober
Akio
A
Kihara
D002518:Ceramides / Q000378:metabolism*; D004795:Enzyme Stability; D005227:Fatty Acids / Q000096:biosynthesis*; D057809:HEK293 Cells; D006367:HeLa Cells; D006720:Homozygote; D006801:Humans; D038901:X-Linked Intellectual Disability / Q000235:genetics*; D020125:Mutation, Missense; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013109:Sphingomyelins / Q000378:metabolism*
D002518:Ceramides; D005227:Fatty Acids; D029701:Saccharomyces cerevisiae Proteins; D013109:Sphingomyelins; D044925:Oxidoreductases Acting on CH-CH Group Donors; C418219:TSC13 protein, S cerevisiae; C434934:trans-2-enoyl-CoA reductase (NADPH)
Fatty Acid; Fatty Acid Metabolism; Lipids; Membrane; Sphingolipid