Singh, Arpita

Description

The thesis work presented here focuses on AKAP18γ mediated multivalent complex formation and its oligomerization. AKAP18γ belongs to a family of structurally diverse but functionally analogous scaffolding proteins called A-Kinase Anchoring Proteins (AKAPs). These scaffolds specifically target Protein Kinase A (PKA) holoenzyme to a distinct cellular compartment to regulate PKA activity and substrate specificity. Previously, the long isoforms of an AKAP called AKAP18 (AKAP18γ/δ) were established as important cardiac calcium regulating proteins due to their ability to mediate phosphorylation of a protein called Phospholamban (PLN). My dissertation work shows that AKAP18γ directly interacts with Inhibitior-1 (I-1) and enhances its phosphorylation under stimulatory conditions. The AKAP18γ-PKA-I-1 complex together regulates Protein Phosphatase 1 (PP1), also found to be associated with this complex. PP1 is a negative regulator of cardiac function due to its ability to dephosphorylate PLN. Based on these results, we propose a model in which AKAP18γ acts as multivalent complex organizing scaffold that may be targeted to the sarcoplasmic reticulum in cardiac myocytes for PLN phosphorylation regulation. This complex may be found in other cell types to regulate PP1 function alone as I-1, PP1 and AKAP18γ have been found in other tissue. Moreover, I also discovered that AKAP18γ is an oligomerizing scaffold and the interaction is isoform specific. A shorter isoform of this gene, AKAP18α does not oligomerize and there is no hetero oligomerization between these isoforms (AKA18α and AKAP18γ). Live cell microscopy shows that AKAP18γ can form heterogenous oligomers ranging from monomers to tetramers in cells. Furthermore, in order...

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Connecticut Digital Archive