| First Author | Spaich S | Year | 2012 |
| Journal | Circ Res | Volume | 111 |
| Issue | 12 | Pages | 1504-16 |
| PubMed ID | 22972877 | Mgi Jnum | J:212883 |
| Mgi Id | MGI:5582384 | Doi | 10.1161/CIRCRESAHA.112.271007 |
| Citation | Spaich S, et al. (2012) F-box and leucine-rich repeat protein 22 is a cardiac-enriched F-box protein that regulates sarcomeric protein turnover and is essential for maintenance of contractile function in vivo. Circ Res 111(12):1504-16 |
| abstractText | RATIONALE: The emerging role of the ubiquitin-proteasome system in cardiomyocyte function and homeostasis implies the necessity of tight regulation of protein degradation. However, little is known about cardiac components of this machinery. OBJECTIVE: We sought to determine whether molecules exist that control turnover of cardiac-specific proteins. METHODS AND RESULTS: Using a bioinformatic approach to identify novel cardiac-enriched sarcomere proteins, we identified F-box and leucine-rich repeat protein 22 (Fbxl22). Tissue-specific expression was confirmed by multiple tissue Northern and Western Blot analyses as well as quantitative reverse-transcriptase polymerase chain reaction on a human cDNA library. Immunocolocalization experiments in neonatal and adult rat ventricular cardiomyocytes as well as murine heart tissue located Fbxl22 to the sarcomeric z-disc. To detect cardiac protein interaction partners, we performed a yeast 2-hybrid screen using Fbxl22 as bait. Coimmunoprecipitation confirmed the identified interactions of Fbxl22 with S-phase kinase-associated protein 1 and Cullin1, 2 critical components of SCF (Skp1/Cul1/F-box) E3- ligases. Moreover, we identified several potential substrates, including the z-disc proteins alpha-actinin and filamin C. Consistently, in vitro overexpression of Fbxl22-mediated degradation of both substrates in a dose-dependent fashion, whereas proteasome inhibition with MG-132 markedly attenuated degradation of both alpha-actinin and filamin C. Finally, targeted knockdown of Fbxl22 in rat cardiomyocytes as well as zebrafish embryos results in the accumulation of alpha-actinin associated with severely impaired contractile function and cardiomyopathy in vivo. CONCLUSIONS: These findings reveal the previously uncharacterized cardiac-specific F-box protein Fbxl22 as a component of a novel cardiac E3 ligase. Fbxl22 promotes the proteasome-dependent degradation of key sarcomeric proteins, such as alpha-actinin and filamin C, and is essential for maintenance of normal contractile function in vivo. |
