Recent structural studies of β-III-spectrin and related cytoskeletal proteins revealed N-terminal sequences that directly bind actin. These sequences are variable in structure, and immediately precede a conserved actin-binding domain composed of tandem calponin homology domains (CH1 and CH2). Here we investigated in Drosophila the significance of the β-spectrin N-terminus, and explored its functional interaction with a CH2-localized L253P mutation that underlies the neurodegenerative disease spinocerebellar ataxia type 5 (SCA5). We report that pan-neuronal expression of an N-terminally truncated β-spectrin fails to rescue lethality resulting from a β-spectrin loss-of-function allele, indicating that the N-terminus is essential to β-spectrin function in vivo. Significantly, N-terminal truncation rescues neurotoxicity and defects in dendritic arborization caused by L253P. In vitro studies show that N-terminal truncation eliminates L253P-induced high-affinity actin binding, providing a mechanistic basis for rescue. These data suggest that N-terminal sequences may be useful therapeutic targets for small molecule modulation of the aberrant actin binding associated with SCA5 β-spectrin and spectrin-related disease proteins.
Bibliographical noteFunding Information:
We thank Cristal Gross, Matthew Hannah, Anne Sophie Heukwa, Mina Juma, Isabelle Lundin, and Nichole Patero for helping with dendritic arbor analyses. This work was supported by Grants from the NIH to AWA (R15NS116511) and to T.S.H. (R01GM044757).
© 2022, The Author(s).
- Animals, Genetically Modified
- Binding Sites
- Drosophila Proteins/genetics
- Drosophila melanogaster/genetics
- Neuronal Plasticity
- Protein Binding
- Protein Interaction Domains and Motifs
- Spinocerebellar Ataxias/genetics
PubMed: MeSH publication types
- Journal Article
- Research Support, N.I.H., Extramural