Spectrin tetramer formation is not required for viable development in Drosophila.
The dominant paradigm for spectrin function is that (αβ)2-spectrin tetramers or higher order oligomers form membrane-associated two-dimensional networks in association with F-actin to reinforce the plasma membrane. Tetramerization is an essential event in such structures. We characterize the tetramerization interaction between α-spectrin and β-spectrins in Drosophila. Wild-type α-spectrin binds to both β- and βH-chains with high affinity, resembling other non-erythroid spectrins. However, α-spec(R22S), a tetramerization site mutant homologous to the pathological α-spec(R28S) allele in humans, eliminates detectable binding to β-spectrin and reduces binding to βH-spectrin ∼1000-fold. Even though spectrins are essential proteins, α-spectrin(R22S) rescues α-spectrin mutants to adulthood with only minor phenotypes indicating that tetramerization, and thus conventional network formation, is not the essential function of non-erythroid spectrin. Our data provide the first rigorous test for the general requirement for tetramer-based non-erythroid spectrin networks throughout an organism and find that they have very limited roles, in direct contrast to the current paradigm.
From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and.
Mansi R
MR
Khanna
From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and.
Floyd J
FJ
Mattie
From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and.
Kristen C
KC
Browder
From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and.
Megan D
MD
Radyk
From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and.
Stephanie E
SE
Crilly
From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and.
Katelyn J
KJ
Bakerink
the Systems Biology Division, The Wistar Institute, Philadelphia, Pennsylvania 19104.
Sandra L
SL
Harper
the Systems Biology Division, The Wistar Institute, Philadelphia, Pennsylvania 19104.
David W
DW
Speicher
From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and gxt5@psu.edu.
Graham H
GH
Thomas
D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism; D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D006801:Humans; D009154:Mutation; D055503:Protein Multimerization; D013049:Spectrin / Q000737:chemistry / Q000235:genetics*
D000199:Actins; D013049:Spectrin
Cell Biology; Cytoskeleton; Drosophila; Membrane Protein; Membrane Skeleton; Protein Assembly; Spectrin