Identification of a novel LXXLL motif in α-actinin 4-spliced isoform that is critical for its interaction with estrogen receptor α and co-activators.
α-Actinins (ACTNs) are a family of proteins cross-linking actin filaments that maintain cytoskeletal organization and cell motility. Recently, it has also become clear that ACTN4 can function in the nucleus. In this report, we found that ACTN4 (full length) and its spliced isoform ACTN4 (Iso) possess an unusual LXXLL nuclear receptor interacting motif. Both ACTN4 (full length) and ACTN4 (Iso) potentiate basal transcription activity and directly interact with estrogen receptor α, although ACTN4 (Iso) binds ERα more strongly. We have also found that both ACTN4 (full length) and ACTN4 (Iso) interact with the ligand-independent and the ligand-dependent activation domains of estrogen receptor α. Although ACTN4 (Iso) interacts efficiently with transcriptional co-activators such as p300/CBP-associated factor (PCAF) and steroid receptor co-activator 1 (SRC-1), the full length ACTN4 protein either does not or does so weakly. More importantly, the flanking sequences of the LXXLL motif are important not only for interacting with nuclear receptors but also for the association with co-activators. Taken together, we have identified a novel extended LXXLL motif that is critical for interactions with both receptors and co-activators. This motif functions more efficiently in a spliced isoform of ACTN4 than it does in the full-length protein.
Department of Biochemistry, Case Western Reserve University and the Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106.
Simran
S
Khurana
Department of Biochemistry, Case Western Reserve University and the Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106.
Sharmistha
S
Chakraborty
Department of Biochemistry, Case Western Reserve University and the Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106.
Xuan
X
Zhao
Department of Biochemistry, Case Western Reserve University and the Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106.
Yu
Y
Liu
Department of Biochemistry, Case Western Reserve University and the Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106.
Dongyin
D
Guan
Comprehensive Cancer Center, Case Western Reserve University and the Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106.
Minh
M
Lam
Center for Proteomics and Department of Pharmacology, School of Medicine, Case Western Reserve University and the Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106.
Wei
W
Huang
Center for Proteomics and Department of Pharmacology, School of Medicine, Case Western Reserve University and the Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106.
Sichun
S
Yang
Department of Biochemistry, Case Western Reserve University and the Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106. Electronic address: hxk43@cwru.edu.
Hung-Ying
HY
Kao
D000185:Actinin / Q000235:genetics / Q000378:metabolism*; D017398:Alternative Splicing / Q000502:physiology*; D020816:Amino Acid Motifs; D045744:Cell Line, Tumor; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D056920:Nuclear Receptor Coactivator 1 / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*; D050880:p300-CBP Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000099224:p300-CBP-Associated Factor
D000185:Actinin; D047628:Estrogen Receptor alpha; D056920:Nuclear Receptor Coactivator 1; D020033:Protein Isoforms; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C111453:ACTN4 protein, human