A vast repertoire of Dscam binding specificities arises from modular interactions of variable Ig domains.
Dscam encodes a family of cell surface proteins required for establishing neural circuits in Drosophila. Alternative splicing of Drosophila Dscam can generate 19,008 distinct extracellular domains containing different combinations of three variable immunoglobulin domains. To test the binding properties of many Dscam isoforms, we developed a high-throughput ELISA-based binding assay. We provide evidence that 95% (>18,000) of Dscam isoforms exhibit striking isoform-specific homophilic binding. We demonstrate that each of the three variable domains binds to the same variable domain in an opposing isoform and identify the structural elements that mediate this self-binding of each domain. These studies demonstrate that self-binding domains can assemble in different combinations to generate an enormous family of homophilic binding proteins. We propose that this vast repertoire of Dscam recognition molecules is sufficient to provide each neuron with a unique identity and homotypic binding specificity, thereby allowing neuronal processes to distinguish between self and nonself.
Wojtowicz
Woj M
WM
Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1662, USA.
Wu
Wei
W
Andre
Ingemar
I
Qian
Bin
B
Baker
David
D
Zipursky
S Lawrence
SL
D017398:Alternative Splicing; D000818:Animals; D001665:Binding Sites; D015815:Cell Adhesion Molecules; D003001:Cloning, Molecular; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008959:Models, Neurological; D009474:Neurons / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D015203:Reproducibility of Results
D015815:Cell Adhesion Molecules; D029721:Drosophila Proteins; C491736:Dscam1 protein, Drosophila; D007135:Immunoglobulin Variable Region; D020033:Protein Isoforms