| Affiliation: | (1) Department of Neurobiology and Anatomy, University of Texas Medical School, 6431 Fannin, Houston, TX 77030, USA;(2) Department of Biochemistry and Molecular Biology, University of Texas Medical School, 6431 Fannin, Houston, TX 77030, USA; |
| Abstract: | Calmodulin (CaM) is a major Ca2+ binding protein involved in two opposing processes of synaptic plasticity of CA1 pyramidal neurons: long-term potentiation (LTP) and depression (LTD). The N- and C-terminal lobes of CaM bind to its target separately but cooperatively and introduce complex dynamics that cannot be well understood by experimental measurement. Using a detailed stochastic model constructed upon experimental data, we have studied the interaction between CaM and Ca2+-CaM-dependent protein kinase II (CaMKII), a key enzyme underlying LTP. The model suggests that the accelerated binding of one lobe of CaM to CaMKII, when the opposing lobe is already bound to CaMKII, is a critical determinant of the cooperative interaction between Ca2+, CaM, and CaMKII. The model indicates that the target-bound Ca2+ free N-lobe has an extended lifetime and may regulate the Ca2+ response of CaMKII during LTP induction. The model also reveals multiple kinetic pathways which have not been previously predicted for CaM-dissociation from CaMKII. |
