Evidence for Aquaporin-mediated Water Transport in Nematocytes of the Jellyfish Pelagia noctiluca

Cellular Physiology and Biochemistry

关键词: Water transport;    Jellyfish;    Pelagia noctiluca;    Aquaporins;    Osmotic swelling;    Volume regulation;    Nematocytes;   

DOI  :  10.1159/000335853

学科分类：分子生物学，细胞生物学和基因

来源: S Karger AG

【 摘 要 】

Nematocytes, the stinging cells of Cnidarians, have a cytoplasm confined to a thin rim. The main cell body is occupied by an organoid, the nematocyst, containing the stinging tubule andvenom. Exposed to hypotonic shock, nematocytes initially swell during an osmotic phase (OP) and then undergo regulatory volume decrease (RVD) driven by K⁺, Cl^- and obligatory water extrusion mechanisms. The purpose of this report is to characterize the OP. Nematocytes were isolated by the NaSCN/Ca²⁺ method from tentacles of the jellyfish Pelagia noctiluca, collected in the Strait of Messina, Italy. Isolated nematocytes were subjected tohyposmotic shock in 65% artificial seawater (ASW) for 15 min. The selective aquaporin water channel inhibitor HgCl₂ (0.1-25 µM) applied prior to osmotic shock prevented the OP and thus RVD. These effects were attenuated in the presence of 1mM dithiothreitol (DTT), a mercaptide bond reducing agent. AgNO₃ (1 µM) and TEA (tetraethylammonium, 100 µM), also reported to inhibit water transport, did not alter the OP but significantly diminished RVD, suggesting different modes of action for the inhibitors tested. Based on estimates of the nematocyte surface area and volume, and OP duration, a relative water permeability of ∼10^-7 cm/sec was calculated and the number of putative aquaporin molecules mediating the OP was estimated. This water permeability is 3-4 orders of magnitude lower in comparison to higher order animals and may constitute an evolutionary advantage for Cnidarian survival.

【 授权许可】

CC BY-NC-ND