D‐AKAP2:PKA RII:PDZK1 ternary complex structure: Insights from the nucleation of a polyvalent scaffold

Abstract

A-kinase anchoring proteins (AKAPs) regulate cAMP-dependent protein kinase (PKA) signaling in space and time. Dual-specific AKAP2 (D-AKAP2/AKAP10) binds with high affinity to both RI and RII regulatory subunits of PKA and is anchored to transporters through PDZ domain proteins. Here, we describe a structure of D-AKAP2 in complex with two interacting partners and the exact mechanism by which a segment that on its own is disordered presents an a-helix to PKA and a b-strand to PDZK1. These two motifs nucleate a polyvalent scaffold and show how PKA signaling is linked to the regulation of transporters. Formation of the D-AKAP2: PKA binary complex is an important first step for high affinity interaction with PDZK1, and the structure reveals important clues toward understanding this phenomenon. In contrast to many other AKAPs, D-AKAP2 does not interact directly with the membrane protein. Instead, the interaction is facilitated by the C-terminus of D-AKAP2, which contains two binding motifs-the D-AKAP2 AKB and the PDZ motif-that are joined by a short linker and only become ordered upon binding to their respective partner signaling proteins. The D-AKAP2 AKB binds to the D/D domain of the R-subunit and the C-terminal PDZ motif binds to a PDZ domain (from PDZK1) that serves as a bridging protein to the transporter. This structure also provides insights into the fundamental question of why D-AKAP2 would exhibit a differential mode of binding to the two PKA isoforms.Keywords: PKA signaling; A-kinase anchoring proteins; D-AKAP2 specificity; AKAP10; PDZK1 crystal structure Additional Supporting Information may be found in the online version of this article.Accession Numbers: The coordinates and the structure factors have been deposited in the RCSB Protein Data Bank (www.rcsb.org) as entry 3TMH.Ganapathy N. Sarma and Issa S. Moody contributed equally to the manuscript.Ganapathy N. Sarma's current address is Bristol-Myers Squibb,

MAP17 Is a Necessary Activator of Renal Na+/Glucose Cotransporter SGLT2

“…31,32 Recently, a crystal structure of a protein complex revealed the molecular details of a three-partner interaction involving the fourth PDZ domain of PDZK1, an A-kinase anchoring protein (D-AKAP2), and its attached PKA. 33 MAP17, through its interaction with PDZK1, has also been shown to play a role in trafficking plasma membrane proteins 18,19 ; hepatic overexpression of MAP17 in mice caused removal of PDZK1 from the plasma membrane along with the attached high-density lipoprotein receptor SR-B1, leading to increased plasma HDL levels. 34 As MAP17 was first cloned on the basis of being overexpressed in tumors, it is not surprising that it has been shown to be an excellent marker for tumorigenesis.…”

Subcellular Organization of the cAMP Signaling Pathway

“…This signalosome may be cell type–dependent, as AKAP2 was not found in the mitochondria at the neuromuscular junction ( Perkins et al, 2001 ). AKAP2 can also interact with components of the cytoskeleton via its C terminus ( Sarma et al, 2015 ), and its overexpression promotes cell growth and is required for calcitonin-mediated migration of cancer cells ( Thakkar et al, 2016 ; Li et al, 2017 ).…”

Cardiac cAMP-PKA Signaling Compartmentalization in Myocardial Infarction

“…In addition to the AKB, the AKAP10 amino acid sequence includes two RGS (Regulators of G protein Signaling) homology domains that interact with the small GTPases Rab4 and Rab11 ( Table 2 ; Figure 2 D). Furthermore, AKAP10 also displays a PDZ (PSD-95/DlgA/ZO-1) binding motif, which docks NHERF (Na + /H + Exchanger Regulatory Factor) isoforms and ensures the connection between the anchoring protein and the solute carrier [ 148 , 179 ]. AKAP10 exhibits a functional single-nucleotide polymorphism (SNP) in which the Ile in position 646 is substituted by a Val [ 165 ].…”