title: Effect of multimeric structure of CaMKII in the GluN2B-mediated modulation of kinetic parameters of ATP.
abstract: Interaction of GluN2B subunit of N-methyl-D-aspartate receptor with calcium/calmodulin dependent protein kinase II (CaMKII) is critical for the induction of long term potentiation at hippocampal CA3-CA1 synapses. We have previously reported that CaMKII binding to GluN2B increases its affinity but abolishes the cooperativity for ATP. In the present study, we demonstrate that the reduction in S(0.5) for ATP of an individual CaMKII subunit seems to be directly induced by the binding of GluN2B to the same subunit, while any GluN2B induced effects on the cooperativity and maximal velocity would additionally require the CaMKII holoenzyme structure. We measured the apparent kinetic parameters for ATP using an association domain truncated monomeric CaMKII and a heteromultimeric CaMKII (having subunits that are either GluN2B binding defective or ATP binding defective), in the presence of GluN2A or GluN2B substrates. The S(0.5) value for ATP of monomeric CaMKII is reduced ∼ 3 fold by the presence of GluN2B suggesting that the induced change in affinity for ATP is independent of the holoenzyme structure. The heteromultimeric mutant of CaMKII, did not exhibit cooperativity of ATP binding probably because of the interspersing of ATP binding defective subunits in the holoenzyme. In contrast to the wild type holoenzyme, presence of GluN2B increased the V(max) of monomeric CaMKII which resulted in an approximately 4.0 fold increase in the apparent catalytic constant (V(max)/S(0.5)) as compared to GluN2A. The kinetic parameter values of the heteromultimeric CaMKII for ATP, on the other hand, did not show any significant difference between the phosphorylation of GluN2B and GluN2A suggesting that modulation requires binding of GluN2B to the same subunit. Overall, our present study provides insights into the role of multimeric structure of CaMKII in GluN2B-mediated regulation.
authors.affiliation: Molecular Neurobiology Division, Rajiv Gandhi Centre for Biotechnology, Thycaud, Thiruvananthapuram, Kerala, India.
authors.forename: John
authors.initials: J
authors.lastname: Cheriyan
authors.forename: Archana G
authors.initials: AG
authors.lastname: Mohanan
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Kurup
authors.forename: Madhavan
authors.initials: M
authors.lastname: Mayadevi
authors.forename: Ramakrishnapillai Vyomakesannair
authors.initials: RV
authors.lastname: Omkumar
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D050505:Mutant Proteins; D011485:Protein Binding; D055503:Protein Multimerization; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D050505:Mutant Proteins; C121001:NR2B NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D000255:Adenosine Triphosphate; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2