Autoregulatory and structural control of CaMKII substrate specificity

dc.contributor.advisorHudmon, Andy
dc.contributor.authorJohnson, Derrick Ethan
dc.contributor.otherHurley, Thomas D.
dc.contributor.otherHoang, Quyen Q.
dc.contributor.otherGallagher, Patricia
dc.date.accessioned2016-10-28T18:29:11Z
dc.date.available2018-10-14T09:30:14Z
dc.date.issued2016-09
dc.degree.date2016en_US
dc.degree.disciplineDepartment of Biochemistry & Molecular Biology
dc.degree.grantorIndiana Universityen_US
dc.degree.levelPh.D.en_US
dc.descriptionIndiana University-Purdue University Indianapolis (IUPUI)en_US
dc.description.abstractCalcium/calmodulin (CaM)-dependent protein kinase II (CaMKII) is a multimeric holoenzyme composed of 8–14 subunits from four closely related isoforms (α, β, γ, δ). CaMKII plays a strategic, multifunctional role in coupling the universal second messenger calcium with diverse cellular processes including metabolism, cell cycle control, and synaptic plasticity. CaMKII exhibits broad substrate specificity, targeting numerous substrates with diverse phosphorylation motifs. Binding of the calcium sensor CaM to the autoregulatory domain (ARD) of CaMKII functions to couple kinase activation with calcium signaling. Important sites of autophosphorylation, namely T287 and T306/7 (δ isoform numbering), reside within the ARD and control either CaM dependence or ability to bind to CaMKII respectively, thus determining various activation states of the kinase. Because autophosphorylation is critical to the function of CaMKII in vivo, we sought to determine the relationship between the activation state of the kinase and substrate selectivity. We show that the ARD of activated CaMKII tunes substrate selectivity by competing for substrate binding to the catalytic domain, thus functioning as a selectivity filter. Specifically, in the absence of T287 autophosphorylation, substrate phosphorylation is limited to high-affinity, consensus substrates. T287 autophosphorylation restores maximal kinase activation and broad substrate selectivity by disengaging ARD filtering. The unique multimeric architecture of CaMKII is an ideal sensor which encodes calcium-spike frequency into graded levels of subunit activation/autophosphorylation within the holoenzyme. We find that differential activation states of the holoenzyme produce distinct substrate phosphorylation profiles. Maximal holoenzyme activation/autophosphorylation leads to further broadening of substrate specificity beyond the effect of autophosphorylation alone, which is consistent with multivalent avidity. Thus, the ability of calcium-spike frequency to regulate T287 autophosphorylation and holoenzyme activation permits cellular activity to dictate switch-like behavior in substrate selectivity that is required for diverse cellular responses by CaMKII.en_US
dc.identifier.doi10.7912/C2V59B
dc.identifier.urihttps://hdl.handle.net/1805/11291
dc.identifier.urihttp://dx.doi.org/10.7912/C2/1781
dc.language.isoen_USen_US
dc.subjectAutophosphorylationen_US
dc.subjectAutoregulationen_US
dc.subjectCaMKIIen_US
dc.subjectPhosphorylationen_US
dc.subjectSubstrate selectivityen_US
dc.titleAutoregulatory and structural control of CaMKII substrate specificityen_US
dc.typeDissertation
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