Purinergic control of lysenin’s transport and voltage-gating properties

• Published in: Purinergic signalling Vol. 12; no. 3; pp. 549 - 559
• Main Authors: Bryant, Sheenah, Shrestha, Nisha, Carnig, Paul, Kosydar, Samuel, Belzeski, Philip, Hanna, Charles, Fologea, Daniel
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-09-2016; Springer Nature B.V
• Subjects: Adenosine; Adenosine Diphosphate - metabolism; Adenosine Monophosphate - metabolism; Adenosine Triphosphate - metabolism; Animals; Biological activity; Biomedical and Life Sciences; Biomedicine; Cancer Research; Channel gating; Channel pores; Conductance; Conduction; Cytolytic activity; Eisenia foetida; Human Physiology; Ion Channel Gating - physiology; Ion Channels - metabolism; Lipid Bilayers - metabolism; Lipid membranes; Neurosciences; Occlusion; Original; Original Article; Patch-Clamp Techniques; Pharmacology/Toxicology; Phosphates; Protein Transport - physiology; Sphingomyelin; Toxins, Biological - metabolism; Voltage; Purinergic control; Adenosine phosphates; Pore-forming toxins; Lysenin; Voltage gating
• ISSN: 1573-9538; 1573-9546
• DOI: 10.1007/s11302-016-9520-9

Lysenin, a pore-forming protein extracted from the coelomic fluid of the earthworm
Eisenia foetida
, manifests cytolytic activity by inserting large conductance pores in host membranes containing sphingomyelin. In the present study, we found that adenosine phosphates control the biological activity of lysenin channels inserted into planar lipid membranes with respect to their macroscopic conductance and voltage-induced gating. Addition of ATP, ADP, or AMP decreased the macroscopic conductance of lysenin channels in a concentration-dependent manner, with ATP being the most potent inhibitor and AMP the least. ATP removal from the bulk solutions by buffer exchange quickly reinstated the macroscopic conductance and demonstrated reversibility. Single-channel experiments pointed to an inhibition mechanism that most probably relies on electrostatic binding and partial occlusion of the channel-conducting pathway, rather than ligand gating induced by the highly charged phosphates. The Hill analysis of the changes in macroscopic conduction as a function of the inhibitor concentration suggested cooperative binding as descriptive of the inhibition process. Ionic screening significantly reduced the ATP inhibitory efficacy, in support of the electrostatic binding hypothesis. In addition to conductance modulation, purinergic control over the biological activity of lysenin channels has also been observed to manifest as changes of the voltage-induced gating profile. Our analysis strongly suggests that not only the inhibitor’s charge but also its ability to adopt a folded conformation may explain the differences in the observed influence of ATP, ADP, and AMP on lysenin’s biological activity.