The Role of Cytoplasmic Domain Contacts in the Functional Relationship Between the Voltage Sensor and Pore of Elk Family Potassium Channels
Open Access
- Author:
- Mancini, Evan
- Area of Honors:
- Biology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Timothy J Jegla, Thesis Supervisor
Sarah Mary Assmann, Thesis Honors Advisor - Keywords:
- PAS domain
S4-S5 linker
potassium ion channels
EAG channels - Abstract:
- Voltage-gated ion channels are a broad class of proteins commonly found in neurons. These proteins can be activated by either hyperpolarized or depolarized membrane potentials and regulate resting membrane potential, membrane resistance, and action potential generation and frequency. This electric current allows neurons to communicate and is the fundamental mechanism of signaling within the nervous system (Kandel et al., 2013). This research investigates the voltage-gated potassium channel human Elk1. The Elk1 subfamily falls within the Ether-a-go-go (EAG) gene family, a group of channels in the CNBD superfamily that are expressed and cardiovascular systems (Codding et al., 2020). The outward potassium current of these channels produces the refractory phase of the action potential. hElk1 channels are comprised of a functionally independent voltage sensor and pore that interact during depolarized membrane potentials to conduct an ion current (Engeland et al., 1998). Past studies have found that when the peptide linkage between these structures (S4-S5 Linker) is severed in other EAG family channels, the channels retain their function with only a minor shift in conductivity. This suggests the presence of other non-covalent interactions that further stabilize the channel (Lorinczi et al., 2015). This research investigates whether physical contact with the N-terminal cytoplasmic Per-Arnt-Sim (PAS) domain attached to the VSD is important for functional association of the VSD and PD in split channels. We attained novel results that hElk1 was still functional when lacking an intact S4-S5 linker and showed only a delay in activation to more depolarized voltages. Consistent with past studies, we also found that hElk1 was able to function with a truncated PAS domain (Li et al., 2015). The severance of the full PAS domain and S4-S5 linker together rendered hElk1 channels nonfunctional, while the severance of only the PAS-cap and the S4-S5 linker expressed a transient inactivating current. We also observed that split channels lacking the PAS domain still trafficked to the membrane, meaning the lack of current in these channels is due to a gating issue. These findings suggest that the PAS domain and S4-S5 linker both contribute to the open state stability of hElk1. However, the exact method of interaction between these structures must be further elucidated. Future research should further elucidate the method of this interaction and investigate interactions between split channels and phospholipid contacts in the cell membrane, specifically PIP2.