Sun, X.R., Badura, A., Pacheco, D.A., Lynch, L.A., Schneider, E.R., Taylor, M.P., Hogue, I.B., Enquist, L.W., Murthy, M., Wang, S.S. (2013). Fast GCaMPs for improved tracking of neuronal activity. Nat. Commun. 4(): 2170.
FlyBase ID
FBrf0222168
Publication Type
Research paper
Abstract
The use of genetically encodable calcium indicator proteins to monitor neuronal activity is hampered by slow response times and a narrow Ca(2+)-sensitive range. Here we identify three performance-limiting features of GCaMP3, a popular genetically encodable calcium indicator protein. First, we find that affinity is regulated by the calmodulin domain's Ca(2+)-chelating residues. Second, we find that off-responses to Ca(2+) are rate-limited by dissociation of the RS20 domain from calmodulin's hydrophobic pocket. Third, we find that on-responses are limited by fast binding to the N-lobe at high Ca(2+) and by slow binding to the C-lobe at lower Ca(2+). We develop Fast-GCaMPs, which have up to 20-fold accelerated off-responses and show that they have a 200-fold range of K(D), allowing coexpression of multiple variants to span an expanded range of Ca(2+) concentrations. Finally, we show that Fast-GCaMPs track natural song in Drosophila auditory neurons and generate rapid responses in mammalian neurons, supporting the utility of our approach.
