Biology subjects

Schulman, H.

Publications and source records attributed to Schulman, H..

3 recordsLinked to original sources

bioRxiv2023

CaMKII autophosphorylation but not downstream kinase activity is required for synaptic memory

CaMKII plays a critical role in long-term potentiation (LTP), a well-established model for learning and memory through the enhancement of synaptic transmission. Biochemical studies indicate that CaMKII catalyzes a phosphotransferase (kinase) reaction of both itself (autophosphorylation) and of multiple downstream target proteins. However, whether either type of phosphorylation plays any role in the synaptic enhancing action of CaMKII remains hotly contested. We have designed a series of experiments to define the minimal requirements for the synaptic enhancement by CaMKII. We find that autophosphorylation of T286 and further binding of CaMKII to the GluN2B subunit are required both for initiating LTP and for its maintenance (synaptic memory). Once bound to the NMDA receptor, the synaptic action of CaMKII occurs in the absence of kinase activity. Thus, autophosphorylation, together with binding to the GluN2B subunit, are the only two requirements for CaMKII in synaptic memory.

neuroscience↗

bioRxiv2019

Flexible linkers in CaMKII control the balance between activating and inhibitory autophosphorylation

The activity of Ca2+/calmodulin-dependent protein kinase II (CaMKII) depends on the balance between activating and inhibitory autophosphorylation (Thr 286 and Thr 305/306, respectively, in the human isoform). Variation in the lengths of the flexible linkers that connect the kinase domains of CaMKII to a central oligomeric hub could alter transphosphorylation rates within a holoenzyme, thereby affecting the balance of autophosphorylation outcomes. Using a single-molecule assay for visualization of CaMKII phosphorylation on glass, we show that the balance of autophosphorylation is flipped between CaMKII- and CaMKII-{beta}, the two principal isoforms in the brain. CaMKII-, with a [~]30 residue kinase-hub linker, readily acquires activating autophosphorylation, which we show is resistant to removal by phosphatases. CaMKII-{beta}, with a [~]200 residue kinase-hub linker, is biased towards inhibitory autophosphorylation. Thus, the responsiveness of CaMKII to calcium signals can be tuned by varying the relative levels of the and {beta} isoforms.

biophysics↗

bioRxiv2019

Conformational coupling by trans-phosphorylation in calcium calmodulin dependent kinase II

The calcium calmodulin dependent protein kinase II (CaMKII) is a dodecameric holoenzyme important for encoding memory. Its activation, triggered by binding of calcium calmodulin, persists autonomously after calmodulin dissociation. One (receiver) kinase captures and subsequently phosphorylates the regulatory domain peptide of a donor kinase forming a chained dimer as a first stage of autonomous activation. Protein dynamics simulations examined the conformational changes triggered by dimer formation and phosphorylation, aimed to provide a molecular rationale for human mutations that result in learning disabilities. Ensembles generated from X-ray crystal structures were characterized by network centrality and community analysis. Mutual information related collective motions to local fragment dynamics encoded with a structural alphabet. Implicit solvent tCONCOORD conformational ensembles revealed the dynamic architecture of Inactive kinase do-mains was co-opted in the activated dimer but the network hub shifted from the nucleotide binding cleft to the captured peptide. Explicit solvent molecular dynamics (MD) showed nucleotide and substrate binding determinants formed coupled nodes in long-range signal relays between regulatory peptides in the dimer. Strain in the extended captured peptide was balanced by reduced flexibility of the receiver kinase C-lobe core. The relays were organized around a hydrophobic patch between the captured peptide and a key binding helix. The human mutations aligned along the relays. Thus, these mutations could disrupt the allosteric network alternatively, or in addition, to altered binding affinities. Non-binding protein sectors distant from the binding sites mediated the allosteric signalling; providing possible targets for inhibitor design. Phosphorylation of the peptide modulated the dielectric of its binding pocket to strengthen the patch, non-binding sectors, domain interface and temporal correlations between parallel relays. These results provide the molecular details underlying the reported positive kinase cooperativity to enrich discussion on how autonomous activation by phosphorylation leads to long-term behavioural effects.

neuroscience↗