Crucial role of copper in detection of metal-coordinating odorants.
Odorant receptors (ORs) in olfactory sensory neurons (OSNs) mediate detection of volatile odorants. Divalent sulfur compounds, such as thiols and thioethers, are extremely potent odorants. We identify a mouse OR, MOR244-3, robustly responding to (methylthio)methanethiol (MeSCH(2)SH; MTMT) in heterologous cells. Found specifically in male mouse urine, strong-smelling MTMT [human threshold 100 parts per billion (ppb)] is a semiochemical that attracts female mice. Nonadjacent thiol and thioether groups in MTMT suggest involvement of a chelated metal complex in MOR244-3 activation. Metal ion involvement in thiol-OR interactions was previously proposed, but whether these ions change thiol-mediated OR activation remained unknown. We show that copper ion among all metal ions tested is required for robust activation of MOR244-3 toward ppb levels of MTMT, structurally related sulfur compounds, and other metal-coordinating odorants (e.g., strong-smelling trans-cyclooctene) among >125 compounds tested. Copper chelator (tetraethylenepentamine, TEPA) addition abolishes the response of MOR244-3 to MTMT. Histidine 105, located in the third transmembrane domain near the extracellular side, is proposed to serve as a copper-coordinating residue mediating interaction with the MTMT-copper complex. Electrophysiological recordings of the OSNs in the septal organ, abundantly expressing MOR244-3, revealed neurons responding to MTMT. Addition of copper ion and chelator TEPA respectively enhanced and reduced the response of some MTMT-responding neurons, demonstrating the physiological relevance of copper ion in olfaction. In a behavioral context, an olfactory discrimination assay showed that mice injected with TEPA failed to discriminate MTMT. This report establishes the role of metal ions in mammalian odor detection by ORs.
Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of National Ministry of Education, Shanghai E-Institute for Chemical Biology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
Xufang
X
Duan
Eric
E
Block
Zhen
Z
Li
Timothy
T
Connelly
Jian
J
Zhang
Zhimin
Z
Huang
Xubo
X
Su
Yi
Y
Pan
Lifang
L
Wu
Qiuyi
Q
Chi
Siji
S
Thomas
Shaozhong
S
Zhang
Minghong
M
Ma
Hiroaki
H
Matsunami
Guo-Qiang
GQ
Chen
Hanyi
H
Zhuang
D000595:Amino Acid Sequence; D000818:Animals; D002412:Cations / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D003300:Copper / Q000502:physiology*; D000242:Cyclic AMP / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D005029:Ethylenediamines / Q000494:pharmacology; D005260:Female; D006639:Histidine / Q000737:chemistry; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D018035:Receptors, Odorant / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012724:Sex Attractants / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013440:Sulfides / Q000378:metabolism*; D013457:Sulfur Compounds / Q000378:metabolism
D002412:Cations; D002614:Chelating Agents; D005029:Ethylenediamines; C571733:MOR244-3 protein, human; C571731:MOR244-3 protein, mouse; D018035:Receptors, Odorant; D012724:Sex Attractants; D013438:Sulfhydryl Compounds; D013440:Sulfides; D013457:Sulfur Compounds; D006639:Histidine; D003300:Copper; D000242:Cyclic AMP; C571732:(methylthio)methanethiol; C034269:tetraethylenepentamine