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FASEB J. 2017 Oct;31(10):4578-4587. doi: 10.1096/fj.201700095R. Epub 2017 Jun 30.

Keratins regulate β-cell mitochondrial morphology, motility, and homeostasis.

Author information

1
Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
2
Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland dtoivola@abo.fi.

Abstract

Loss of the epithelial intermediate filament protein keratin 8 (K8) in murine β cells leads to irregular insulin vesicles and decreased insulin levels. Because mitochondria are central in glucose-stimulated insulin secretion, the relationship between keratins and β-cell mitochondrial function and morphology was investigated. β cells in murine K8-knockout (K8-/-) islets of Langerhans have increased numbers of mitochondria, which are rounder and have diffuse cristae, as seen by electron microscopy. The mitochondrial network in primary cultured K8-/- β cells is more fragmented compared with K8+/+ mitochondria, correlating with decreased levels of mitofusin 2 and the mitofusin 2- and keratin-binding protein trichoplein. K8-/- β-cell mitochondria have decreased levels of total and mitochondrial cytochrome c, which correlates with a reduction in electron transport complexes I and IV. This provokes loss of mitochondrial membrane potential and reduction of ATP and insulin amount, as seen in K8-/- β cells. Mitochondria in K8 wild-type β cells and MIN6 insulinoma cells overexpressing K8 and 18 are more stationary compared with mitochondria in keratin-deficient cells. In conclusion, keratins, likely through trichoplein-mitofusin interactions, regulate both structural and dynamic functions of β-cell mitochondria, which could have implications for downstream insulin secretion.-Silvander, J. S. G., Kvarnström, S. M., Kumari-Ilieva, A., Shrestha, A., Alam, C. M., Toivola, D. M. Keratins regulate β-cell mitochondrial morphology, motility, and homeostasis.

KEYWORDS:

K8-null mice; TEM; fusion; insulin secretion; islets

PMID:
28666985
DOI:
10.1096/fj.201700095R
[Indexed for MEDLINE]

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