The Rise and Fall of TRP-N, an Ancient Family of Mechanogated Ion Channels, in Metazoa.
Bottom Line: In flies, the transient-receptor-potential N protein (TRP-N) was found to be a cilia-associated mechanoreceptor.We propose that these new candidate proteins help explain the sensory complexity of Cnidaria which has been previously observed but so far has lacked a molecular underpinning.Also, the ancient appearance of TRP-N supports a common origin of important components of the nervous systems in Ctenophores, Cnidaria, and Bilateria.
Affiliation: Institute for Evolution and Biodiversity, University of Muenster, Germany.Show MeSH
Mentions: TRP-N has a long N-terminal ankyrin-repeat which comprises approximately 28 ankyrin domains. This repeat has been conjectured to be the gating spring which is involved in the transmission of mechanical force to the transmembrane domain (Howard and Bechstedt 2004; Liang et al. 2013). The ankyrin domains in this repeat presumably form a superhelix as they arrange into a complete turn which can be easily deformed mechanically. Ankyrin domains are widespread across proteins with very different functions and occur in 0.85% of all metazoan proteins. However, the average number of ankyrin domains across all ankyrin-containing proteins is only 4.8 (±4.5, median 3), and proteins with more than ten ankyrin domains are rare (Jernigan and Bordenstein 2014) (see also fig. 1). Note that determining the precise number of domains in a domain repeat is a difficult problem. The underlying reasons are inaccuracies arising during sequencing and assembly, and rapid evolutionary changes of sequences and number of domains, even at the population level. Finally, computational challenges are common, for example, in the frame capturing of the domains in a repeat (Schaper et al. 2012). Consequently, even the most accurate programs may fail to determine the number of domains in a repeat by a number of 1. We will, in the following work, always use the lower number of prediction, for example, 28 if there might be 28 or 29 domains in a repeat.Fig. 1.—
Affiliation: Institute for Evolution and Biodiversity, University of Muenster, Germany.