Enhancement of the Olfactory Response by Lipocalin Cp-Lip1 in Newt Olfactory Receptor Cells: An Electrophysiological Study. (26th July 2019)

• Record Type: Journal Article
• Authors: Nakamura, Tadashi; Noumi, Yoshihiro; Yamakawa, Hiroyuki; Nakamura, Atsushi; Wen, Durige; Li, Xing; Geng, Xiong; Sawada, Ken; Iwasa, Tatsuo
• Is Part Of: Chemical senses. Volume 44:Number 7(2019)
• Page Start: 523
• Page End: 533
• Publication Date: 2019-07-26
• Subjects: action potential -- electro-olfactography -- odorant-binding protein -- suction electrode; Chemical senses -- Periodicals; 612.8
• DOI: 10.1093/chemse/bjz048
• Languages: English
• ISSNs: 0379-864X

Abstract

Abstract: Previously, we have detected the expression of 2 lipocalin genes (lp1 and lp2) in the olfactory epithelium of the Japanese newt Cynops pyrrhogaster. Recombinant proteins of these genes (Cp-Lip1 and Cp-Lip2, respectively) exhibited high affinities to various odorants, suggesting that they work like the odorant-binding proteins (OBPs). However, the physiological functions of OBP generally remain inconclusive. Here, we examined the effect of Cp-Lip1 on the electrophysiological responses of newt olfactory receptor cells. We observed that the electro-olfactogram induced by the vapor of an odorant with high affinity to Cp-Lip1 appeared to increase in amplitude when a tiny drop of Cp-Lip1 solution was dispersed over the olfactory epithelium. However, the analysis was difficult because of possible interference by intrinsic components in the nasal mucus. We subsequently adopted a mucus-free condition by using suction electrode recordings from isolated olfactory cells, in which impulses were generated by puffs of odorant solution. When various concentration (0–5 µM) of Cp-Lip1 was mixed with the stimulus solution of odorants highly affinitive to Cp-Lip1, the impulse frequency increased in a concentration-dependent manner. The increase by Cp-Lip1 was seen more evidently at lower concentration ranges of stimulus odorants. These results strongly suggest that Cp-Lip1 broadens the sensitivity of the olfactory cells toward the lower concentration of odorants, by which animals can detect very low concentration of odorants.