A research group led by Hajime Fujii and Haruhiko Bito at the Department of Neurochemistry, Graduate School of Medicine, the University of Tokyo, has developed a novel imaging platform, dFOMA or dual FRET with Optical MAnipulation, and examined how the information contained in the frequency and number of neurotransmitter releases is transformed into postsynaptic Ca2+ signaling.
Their results uncover striking rules performed by femto-nanoliter spaces near and at the synapse of neurons. Thus, Ca2+/CaM-dependent synaptic enzymes, such as CaMKII and calcineurin, are activated through non-linear decoding mechanisms.
CaMKIIα activity sums supralinearly and senses both higher frequency and input number, acting as an input frequency/number decoder. In contrast, calcineurin activity summates sublinearly with increasing input number and shows little frequency-dependence, thus functioning as an input number counter.
These results provide evidence that CaMKIIα and calcineurin are fine-tuned to unique bandwidths and compute input variables in an asymmetric manner. Deciphering the enzymatic information processing at synapses provides a better understanding of the signaling machineries underlying synaptic plasticity and learning and memory.
Source: University of Tokyo