Identification and characterization of Fbxl22, a novel skeletal muscle atrophy-promoting E3 ubiquitin ligase

Authors

David C. Hughes, University of Iowa Carver College of Medicine
Leslie M. Baehr, University of Iowa Carver College of MedicineFollow
Julia R. Driscoll, University of North Florida
Sarah A. Lynch, University of North Florida
David S. Waddell, University of North FloridaFollow
Sue C. Bodine, University of Iowa Carver College of MedicineFollow

Document Type

Article

Publication Date

10-1-2020

Abstract

Muscle-specific E3 ubiquitin ligases have been identified in muscle atrophy-inducing conditions. The purpose of the current study was to explore the functional role of F-box and leucine-rich protein 22 (Fbxl22), and a newly identified splice variant (Fbxl22-193), in skeletal muscle homeostasis and neurogenic muscle atrophy. In mouse C2C12 muscle cells, promoter fragments of the Fbxl22 gene were cloned and fused with the secreted alkaline phosphatase reporter gene to assess the transcriptional regulation of Fbxl22. The tibialis anterior muscles of male C57/BL6 mice (12-16 wk old) were electroporated with expression plasmids containing the cDNA of two Fbxl22 splice variants and tissues collected after 7, 14, and 28 days. Gastrocnemius muscles of wild-type and muscle-specific RING finger 1 knockout (MuRF1 KO) mice were electroporated with an Fbxl22 RNAi or empty plasmid and denervated 3 days posttransfection, and tissues were collected 7 days postdenervation. The full-length gene and novel splice variant are transcriptionally induced early (after 3 days) during neurogenic muscle atrophy. In vivo overexpression of Fbxl22 isoforms in mouse skeletal muscle leads to evidence of myopathy/atrophy, suggesting that both are involved in the process of neurogenic muscle atrophy. Knockdown of Fbxl22 in the muscles of MuRF1 KO mice resulted in significant additive muscle sparing 7 days after denervation. Targeting two E3 ubiquitin ligases appears to have a strong additive effect on protecting muscle mass loss with denervation, and these findings have important implications in the development of therapeutic strategies to treat muscle atrophy.

Publication Title

American Journal of Physiology - Cell Physiology

Volume

319

Issue

4

First Page

C700

Last Page

C719

Digital Object Identifier (DOI)

10.1152/ajpcell.00253.2020

PubMed ID

32783651

ISSN

03636143

E-ISSN

15221563

Citation Information

Hughes, D.C., Baehr, L.M., Driscoll, J.R., Lynch, S.A., Waddell, D.S., Bodine, S.C. (2020) Identification and Characterization of Fbxl22, a Novel Skeletal Muscle Atrophy-promoting E3 Ubiquitin Ligase. American Journal of Physiology - Cell Physiology, 319(4), C700-C719.