A Comparison of the Polycation Receptors of Paramecium tetraurelia and Tetrahymena thermophila

Abstract

Chemorepellents are compounds that cause ciliated protozoans to reorient their swimming direction. A number of chemorepellents have been studied in the ciliated protozoans, Paramecium and Tetrahymena. Chemorepellents, such as polycations, cause the organism to exhibit "avoidance behavior," a swimming behavior characterized by jerky movements and other deviations from normal forward swimming, which result from ciliary reversal. One well-characterized chemorepellent pathway in Tetrahymena is that of the proposed polycation receptor that is activated by lysozyme and pituitary adenylate cyclase activating polypeptide (PACAP). In this study, we compare the response of Paramecium to the chemorepellents lysozyme, vasoactive intestinal peptide (VIP), and PACAP to the previously studied polycation response in Tetrahymena. Our results indicate that lysozyme, VIP, and PACAP are all chemorepellents in Paramecium, just as they are in Tetrahymena. However, the signaling pathways involved appear to be different. While previous pharmacological characterization indicates that G-proteins are involved in polycation signaling in Tetrahymena, we present evidence that similar reception in Paramecium involves activation of a tyrosine kinase pathway in order for lysozyme avoidance to occur. Polycation responses of both organisms are inhibited by neomycin sulfate. While PACAP is the most effective of the three chemorepellents in Tetrahymena, lysozyme is the most effective chemorepellent in Paramecium.

Eukaryotic inhibitors or activators elicit responses to chemosensory compounds by ruminal isotrichid and entodiniomorphid protozoa

“…Because no rumen protozoan genome has yet been sequenced to our knowledge, limiting expression-based approaches, we used motility assays to verify chemotaxis results (Hennessey and Lampert, 2012). In experiment 4, based on our prior study (Diaz et al, 2014b), we Bartholomew et al, 2008;Robinette et al, 2008;Lampert et al, 2011) and inositide signaling pathways (panel B; Leondaritis et al, 2011) to explain physiology by ruminal ciliates based on responses from Paramecium and Tetrahymena. In panel A, sugars and amino acids bind to external receptors (left), which should transduce (dashed arrow) respective receptors coupled to a transmembrane tyrosine kinase (RTK) or a G-protein (GPCR), which should open a Ca 2+ channel at the plasma membrane and (or) activate phospholipase C (PLC).…”

Netrin-1 Peptide Is a Chemorepellent inTetrahymena thermophila

“…Controls (netrin-1 adapted to netrin-1, PACAP adapted to PACAP, and GTP adapted to GTP) showed only baseline avoidance, indicating that adaptation to these compounds was occurring. Baseline avoidance in our behavioral studies indicates the amount of avoidance typically seen when moving cells from a well containing behavioral buffer to another well containing the same buffer and ranges from about 7 to 20% ([ 8 , 11 , 12 ], current study). This is how baseline avoidance is defined in the pharmacological studies as well.…”

“…Behavioral assays were carried out as previously described [ 8 , 9 , 11 – 13 ]. Tetrahymena thermophila was washed 3 times in behavioral buffer and then 300 μ L of cell suspension was transferred to the first well of a microtiter plate.…”

Nociceptin Signaling Involves a Calcium-Based Depolarization in Tetrahymena thermophila

“…Behavioral assays were carried out as previously described [8, 10, 17]. Ten milliliters of T. thermophila culture was washed by centrifugation in a clinical centrifuge at high speed, and the pellet was reconstituted in 10 mL buffer.…”

“…Cross-adaptation assays were performed as previously described [10, 17]. Briefly, 300  μ L of cells were placed into the first well of a 3-well microtiter plate.…”