Kinetic evaluation of photosensitivity in genetically engineered neurons expressing green algae light-gated channels.
Neurons become photosensitive by genetically introducing one of green algae-derived protein, channelrhodopsin-2 (ChR2). Here, we quantitatively investigated the rapidness of the light-gated current of ChR2 expressed in PC12 cells using blue light-emitting diode (LED) light. The light-gated current consists of two components, inactivating and non-inactivating. The magnitude of inactivating component was almost linearly related to the light intensity. The non-inactivating component showed a tendency to saturate at high illumination. Both the activation and inactivation rates of the light-gated current were linearly dependent on the light intensity. However, the activation rate (turning-on rate) is about 10-fold faster than the inactivation rate. Although the turning-off time constant was little dependent on the light intensity, that at the end of 1s light pulse was about two-fold larger than that at 20 ms. Neurons are also made photosensitive by the expression of ChR2 in the living animal. Since both the turning-on and turning-off time constants of light-gated current was smaller than the membrane time constant of neurons, the LED light illumination of the photosensitive neurons was enough to evoke action potentials in a pulse-to-pulse manner in an acute slice of hippocampus.
Ishizuka
Toru
T
Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, 2-1 Seiryo-machi, Sendai 980-8575, Japan.
Kakuda
Masaaki
M
Araki
Rikita
R
Yawo
Hiromu
H
D000465:Algorithms; D000818:Animals; D000460:Chlorophyta / Q000378:metabolism*; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D005818:Genetic Engineering; D006624:Hippocampus / Q000166:cytology; D015640:Ion Channel Gating / Q000502:physiology* / Q000528:radiation effects; D007473:Ion Channels / Q000096:biosynthesis / Q000235:genetics* / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000502:physiology* / Q000528:radiation effects*; D016716:PC12 Cells; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D010777:Photochemistry; D051381:Rats; D012243:Rhodopsin / Q000378:metabolism; D012845:Sindbis Virus / Q000235:genetics; D014162:Transfection
D018076:DNA, Complementary; D007473:Ion Channels; D012243:Rhodopsin