Routing of Kv7.1 to endoplasmic reticulum plasma membrane junctions

• Published in: Acta Physiologica Vol. 240; no. 3; pp. e14106 - n/a
• Main Authors: Serrano‐Novillo, Clara, Estadella, Irene, Navarro‐Pérez, María, Oliveras, Anna, Benito‐Bueno, Angela, Socuéllamos, Paula G., Bosch, Manel, Coronado, María José, Sastre, Daniel, Valenzuela, Carmen, Soeller, Christian, Felipe, Antonio
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01-03-2024
• Subjects: Action potential; adaptors; Biotin; Cell surface; cell surface targeting; Electrophysiology; Endoplasmic reticulum; ERPMj inducers; Golgi apparatus; Heart; Immunocytochemistry; Membrane junctions; Microscopy; Plasma; potassium channels; Potassium channels (voltage-gated); Proteins; Proteomics; Transmission electron microscopy; ERPMj inducers; adaptors; cell surface targeting; potassium channels
• ISSN: 1748-1708; 1748-1716; 1748-1716
• DOI: 10.1111/apha.14106

Aim
The voltage‐gated Kv7.1 channel, in association with the regulatory subunit KCNE1, contributes to the IKs current in the heart. However, both proteins travel to the plasma membrane using different routes. While KCNE1 follows a classical Golgi‐mediated anterograde pathway, Kv7.1 is located in endoplasmic reticulum‐plasma membrane junctions (ER‐PMjs), where it associates with KCNE1 before being delivered to the plasma membrane.
Methods
To characterize the channel routing to these spots we used a wide repertoire of methodologies, such as protein expression analysis (i.e. protein association and biotin labeling), confocal (i.e. immunocytochemistry, FRET, and FRAP), and dSTORM microscopy, transmission electron microscopy, proteomics, and electrophysiology.
Results
We demonstrated that Kv7.1 targeted ER‐PMjs regardless of the origin or architecture of these structures. Kv2.1, a neuronal channel that also contributes to a cardiac action potential, and JPHs, involved in cardiac dyads, increased the number of ER‐PMjs in nonexcitable cells, driving and increasing the level of Kv7.1 at the cell surface. Both ER‐PMj inducers influenced channel function and dynamics, suggesting that different protein structures are formed. Although exhibiting no physical interaction, Kv7.1 resided in more condensed clusters (ring‐shaped) with Kv2.1 than with JPH4. Moreover, we found that VAMPs and AMIGO, which are Kv2.1 ancillary proteins also associated with Kv7.1. Specially, VAP B, showed higher interaction with the channel when ER‐PMjs were stimulated by Kv2.1.
Conclusion
Our results indicated that Kv7.1 may bind to different structures of ER‐PMjs that are induced by different mechanisms. This variable architecture can differentially affect the fate of cardiac Kv7.1 channels.