442: When pumps go missing: Ca2+ control of PMCA2 in Tmc1 deafness mutants

Rolseth AB et al., Proceedings of the National Academy of Sciences (PNAS) - This study links reduced Ca2+ entry through mutant TMC1 mechanotransducer channels to decreased PMCA2 pump density in outer hair cell stereocilia. PMCA2 turnover is rapid in the early postnatal period and is regulated by stereociliary Ca2+ via insertion from an apical vesicular pool; Neuroplastin (NPTN) later stabilizes the pump complex. Persistent pump reduction at hearing onset may contribute to hair cell mitochondrial dysfunction and death in Tmc1 mutants. Key terms: TMC1, PMCA2, hair cells, Ca2+ regulation, neuroplastin.

Study Highlights:
Tmc1 point mutations that reduce MET channel Ca2+ permeability show markedly decreased PMCA2 immunolabeling in outer hair cell bundles. PMCA2 density scaled with calculated Ca2+ entry, and experimental lowering of extracellular Ca2+ or pharmacological block of endocytosis or PtdIns(4,5)P2 synthesis reduced PMCA2 during the first postnatal week. PMCA2 is supplied from an apical vesicular pool, turns over rapidly before P11, and NPTN expression lags PMCA2 by ~2 days and less Ca2+ sensitivity, consistent with a stabilizing accessory role. The lower PMCA2 density persists at hearing onset and may contribute to mitochondrial dysfunction and subsequent hair cell death.

Conclusion:
Reduced stereociliary Ca2+ influx through mutant TMC1 channels decreases Ca2+-regulated insertion and rapid turnover of PMCA2 from an apical vesicular pool during early postnatal development. Because PMCA2 becomes less plastic after ~P11 and NPTN-mediated stabilization follows PMCA2 expression, early pump loss is maintained into hearing onset and may exacerbate intracellular Ca2+ dysregulation, mitochondrial impairment, and hair cell apoptosis in Tmc1 mutants.

Music:
Enjoy the music based on this article at the end of the episode.

Article title:
Ca2+ regulation of PMCA2 calcium pump expression in hair cells of Tmc1 deafness mutants

First author:
Rolseth AB

Journal:
Proceedings of the National Academy of Sciences (PNAS)

DOI:
10.1073/pnas.2607733123

Reference:
Rolseth AB, Beurg M, Konrad DE, Augusta BK, Fettiplace R. Ca2+ regulation of PMCA2 calcium pump expression in hair cells of Tmc1 deafness mutants. Proc Natl Acad Sci U.S.A. 2026;123:e2607733123. doi:10.1073/pnas.2607733123.

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/

Support:
Base by Base is independent and ad-free — no sponsors, no paywall. If an episode was worth your time, chip in and keep the papers audited and the original songs coming:
❤️ Support monthly: https://buy.stripe.com/cNifZhclVebvagk2JDgEg01
☕ One-time donation: https://donate.stripe.com/7sY4gz71B2sN3RWac5gEg00
More at basebybase.com

On PaperCast Base by Base you'll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Episode link: https://basebybase.com/episodes/ca2-regulation-pmca2-tmc1

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-08-17.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the core scientific narrative in the transcript: MET Ca2+ permeability reductions in Tmc1 mutants, Ca2+-dependent PMCA2 regulation and vesicle trafficking, dynamic turnover and endocytosis, NPTN's stabilizing role, pharmacological perturbations (Pitstop2, PAO, GSK-1), endolymphatic potential effects at hearing
- transcript topics: MET channel Ca2+ permeability in Tmc1 mutants; PMCA2 density regulation and Ca2+ entry relationship; Ca2+-dependent PMCA2 turnover and vesicle tra...