KCNK15

KCNK15 (TASK-5) is a two-pore domain potassium channel subunit that is electrically silent as a homodimer but functions as a modulatory partner in heterodimeric complexes with TASK-1 and TASK-3. When expressed alone in heterologous systems, TASK-5 does not produce plasma membrane K⁺ currents, a deficiency mapped to its M1–M3 domain rather than to ER retention (PMID:11409881, PMID:11680614, PMID:11749039). TASK-5 forms functional heterodimers with TASK-1 and TASK-3 at the plasma membrane, where it negatively modulates their surface expression and alters single-channel conductance, Gq-coupled receptor inhibition, and pharmacological sensitivity, with a common KCNK15 polymorphism further affecting heterodimer pharmacology (PMID:39215006). In the auditory brainstem, TASK-5 contributes to resting membrane potential in cochlear nucleus and trapezoid body neurons, and its loss alters neuronal excitability and auditory brainstem responses to loud sounds (PMID:39553828).

1. 2001 High

   Establishing that TASK-5 is a non-functional K2P channel subunit resolved the paradox of a channel gene that produces no measurable current, directing attention to its potential role as a regulatory subunit rather than a conventional pore-forming channel.

   Evidence Heterologous expression in COS-7 cells and Xenopus oocytes by three independent groups; chimeric TASK-5/TASK-3 constructs localizing the non-functional region to M1–M3; truncation mutagenesis excluding ER retention as the cause

   PMID:11409881 PMID:11680614 PMID:11749039

   Open questions at the time

   • No endogenous function or native binding partner identified
   • Structural basis for non-functionality of the M1–M3 domain not resolved
   • Early co-expression with TASK-1 failed to detect heteromerization, leaving open whether TASK-5 partners with other K2P subunits
2. 2021 Medium

   Discovery that the antisense lncRNA KCNK15-AS1 directly suppresses KCNK15 translation by binding its 5′UTR revealed a specific post-transcriptional regulatory layer controlling KCNK15 protein levels.

   Evidence RNA pulldown, luciferase reporter assay, co-immunoprecipitation, and ubiquitination assays in pancreatic cancer cell lines

   PMID:34853296

   Open questions at the time

   • Functional consequences of KCNK15 translational suppression on channel activity not assessed
   • Relevance of KCNK15-AS1 regulation outside pancreatic cancer cells not tested
   • Single-lab study without independent replication
3. 2024 High

   Demonstration that TASK-5 forms functional heterodimeric complexes with TASK-1 and TASK-3 overturned the earlier conclusion that TASK-5 cannot heteromerize, and established its role as a negative modulator of TASK channel surface expression, conductance, and pharmacology.

   Evidence Co-immunoprecipitation, single-channel electrophysiology, surface expression quantification, and pharmacological profiling in heterologous cells

   PMID:39215006

   Open questions at the time

   • Native tissue co-expression and heterodimer stoichiometry not determined
   • Structural mechanism by which TASK-5 reduces surface expression of TASK channels is unknown
   • Impact of the KCNK15 polymorphism on in vivo channel function not tested
4. 2024 High

   Task5 knockout mice revealed that the channel contributes to resting membrane potential and excitability in auditory brainstem neurons, linking the subunit to a specific physiological role in sound processing.

   Evidence Knock-out mouse model with whole-cell patch-clamp recordings and auditory brainstem response measurements

   PMID:39553828

   Open questions at the time

   • Identity of the native heterodimeric partner(s) of TASK-5 in auditory neurons not established
   • Whether auditory phenotype reflects loss of TASK-5 homodimeric or heterodimeric function is unclear
   • Behavioral consequences (e.g., sound localization deficits) not assessed

• The structural basis for TASK-5 homodimer non-functionality and the identity of its native heterodimeric partners in specific tissues remain unresolved, as does whether TASK-5 modulation of TASK channels is relevant to human auditory or other neurological disorders.
• No crystal or cryo-EM structure of TASK-5 or its heterodimers available
• Native heterodimeric partner identity in auditory brainstem not confirmed
• No human genetic disease linkage established through direct evidence