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bioRxiv · 10.1101/2024.07.16.603652

All-optical mapping of Ca2+ transport and homeostasis in dendrites

Hayward, R. F.·Cohen, A. E.
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Abstract

Calcium mediates many important signals in dendrites. However, the basic transport properties of calcium in dendrites have been difficult to measure: how far and how fast does a local influx of calcium propagate? We developed an all-optical system for simultaneous targeted Ca2+ import and concentration mapping. We co-expressed a blue light-activated calcium selective channelrhodopsin, CapChR2, with a far-red calcium sensor, FR-GECO1c, in cultured rat hippocampal neurons, and used patterned optogenetic stimulation to introduce calcium into cells with user-defined patterns of space and time. We determined a mean steady-state length constant for Ca2+ transport{phi} [~] 5.8 m, a half-life for return to baseline t1/2 [~] 1.7 s, and an effective diffusion coefficient D [~] 20 m2/s, though there were substantial differences in Ca2+ dynamics between proximal and distal dendrites. At high Ca2+ concentration, distal dendrites showed nonlinear activation of Ca2+ efflux, which we pharmacologically ascribed to the NCX1 antiporter. Genetically encoded tools for all-optical study of Ca2+ transport and handling provide a powerful capability for studying this important messenger.

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Hayward, R. F., Cohen, A. E.. 2024-07-19. All-optical mapping of Ca2+ transport and homeostasis in dendrites. https://doi.org/10.1101/2024.07.16.603652

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