The Journal of Neuroscience, August 1, 2001, 21(15):5693-5702
Exploration of Signal Transduction Pathways in Cerebellar
Long-Term Depression by Kinetic Simulation
Shinya
Kuroda1, 2,
Nicolas
Schweighofer1, and
Mitsuo
Kawato1, 3
1 Kawato Dynamic Brain Project, ERATO, Japan
Science and Technology, Kyoto 619-0288, Japan, 2 Division
of Signal Transduction, Nara Institute of Science and Technology, Ikoma
630-0101, Japan, and 3 ATR, Kyoto 619-0288, Japan
Because multiple molecular signal transduction pathways regulate
cerebellar long-term depression (LTD), which is thought to be a
possible molecular and cellular basis of cerebellar learning, the
systematic relationship between cerebellar LTD and the currently known
signal transduction pathways remains obscure. To address this issue, we
built a new diagram of signal transduction pathways and developed a
computational model of kinetic simulation for the
phosphorylation of AMPA receptors, known as a key step for expressing cerebellar LTD. The phosphorylation of AMPA receptors in
this model consists of an initial phase and an intermediate phase. We
show that the initial phase is mediated by the activation of linear
cascades of protein kinase C (PKC), whereas the intermediate phase is
mediated by a mitogen-activated protein (MAP) kinase-dependent positive
feedback loop pathway that is responsible for the transition from the
transient phosphorylation of the AMPA receptors to the stable
phosphorylation of the AMPA receptors. These phases are dually
regulated by the PKC and protein phosphatase pathways. Both phases also
require nitric oxide (NO), although NO per se does not show any ability
to induce LTD; this is consistent with a permissive role as reported
experimentally (Lev-Ram et al., 1997). Therefore, the kinetic
simulation is a powerful tool for understanding and exploring the
behaviors of complex signal transduction pathways involved in
cerebellar LTD.
Key words:
cerebellar long-term depression; kinetics; simulation; signal transduction; positive feedback loop; phosphorylation
Copyright © 2001 Society for Neuroscience 0270-6474/01/21155693-10$05.00/0