Reduced cellular expression and activity of the P129T mutant of human fatty acid amide hydrolase: evidence for a link between defects in the endocannabinoid system and problem drug use.
Fatty acid amide hydrolase (FAAH) inactivates the endogenous cannabinoid (endocannabinoid) anandamide and related lipid transmitters in vivo. A single nucleotide polymorphism (SNP) in the human FAAH gene (385C to A) has recently been described that, in homozygous form, is over-represented in subjects with problem drug use. This SNP, which converts a conserved proline residue in FAAH to threonine (P129T), suggests a potential role for the FAAH-endocannabinoid system in regulating addictive behavior. Nonetheless, the impact of the 385A mutation on the biochemical and cellular function of FAAH remains unknown. Here, we report that T-lymphocytes isolated from patients homozygous for the P129T-FAAH variant express less than half of the FAAH protein and activity observed in wild-type (WT) lymphocytes. Transfected COS-7 cells also expressed significantly lower levels of P129T-FAAH compared with WT-FAAH, indicating that the aberrant expression of the former protein is not a cell type-specific phenomenon. A comparison of the transcription/translation efficiencies and cellular stabilities of WT- and P129T-FAAH proteins revealed that the reduced expression of the mutant enzyme is due to a post-translational mechanism that precedes productive folding. These findings indicate that the natural 385A SNP in the human FAAH gene produces a mutant enzyme with reduced cellular stability, thus fortifying a potential link between functional abnormalities in the endocannabinoid system and drug abuse and dependence.
Chiang
Kyle P
KP
The Skaggs Institute for Chemical Biology and Department of Cell Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd, La Jolla, CA 92037, USA.
Gerber
Alexandra L
AL
Sipe
Jack C
JC
Cravatt
Benjamin F
BF
D000581:Amidohydrolases / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D063385:Cannabinoid Receptor Modulators / Q000378:metabolism; D002522:Chlorocebus aethiops; D063388:Endocannabinoids; D015870:Gene Expression; D006207:Half-Life; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011487:Protein Conformation; D019966:Substance-Related Disorders / Q000201:enzymology* / Q000235:genetics*; D013601:T-Lymphocytes / Q000737:chemistry / Q000378:metabolism; D014162:Transfection; D000099252:Fatty Acid Amide Hydrolases
D000581:Amidohydrolases; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D046988:Proteasome Endopeptidase Complex; D000099252:Fatty Acid Amide Hydrolases