Keratins and Plakin family cytolinker proteins control the length of epithelial microridge protrusions

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Abstract

Actin filaments and microtubules create diverse cellular protrusions, but intermediate filaments, the strongest and most stable cytoskeletal elements, are not known to directly participate in the formation of protrusions. Here we show that keratin intermediate filaments directly regulate the morphogenesis of microridges, elongated protrusions arranged in elaborate maze-like patterns on the surface of mucosal epithelial cells. We found that microridges on zebrafish skin cells contained both actin and keratin filaments. Keratin filaments stabilized microridges, and overexpressing keratins lengthened them. Envoplakin and Periplakin, Plakin family cytolinkers that bind F-actin and keratins, localized to microridges and were required for their morphogenesis. Strikingly, Plakin protein levels directly dictated microridge length. An actin-binding domain of Periplakin was required to initiate microridge morphogenesis, whereas Periplakin-keratin binding was required to elongate microridges. These findings separate microridge morphogenesis into distinct steps, expand our understanding of intermediate filament functions, and identify microridges as protrusions that integrate actin and intermediate filaments.

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All data generated or analyzed during this study are included in the manuscript and supporting files.

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Yasuko Inaba

Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, United States

For correspondence
yasuko.nam@gmail.com

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-3239-2075
Vasudha Chauhan

Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, United States

Competing interests
The authors declare that no competing interests exist.
Aaron Paul van Loon

Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, United States

Competing interests
The authors declare that no competing interests exist.
Lamia Saiyara Choudhury

Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, United States

Competing interests
The authors declare that no competing interests exist.
Alvaro Sagasti

Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, United States

For correspondence
sagasti@mcdb.ucla.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-6823-0692

Funding

NIGMS (R01GM122901)

Alvaro Sagasti

NEI (R21EY024400)

Alvaro Sagasti

NIGMS (GM007185)

Aaron Paul van Loon

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Animal experimentation: All animal experimental procedures were approved by the Chancellor's Animal Research Care Committee at UCLA (protocol #2005-117-41D).

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.