Type II Regulatory Subunits are not Required for the Anchoring-Dependent Modulation of Ca2+Channel Activity by cAMP-Dependent Protein Kinase

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 94; no. 20; pp. 11067 - 11072
• Main Authors: Burton, Kimberly A., Johnson, Barry D., Hausken, Zachary E., Westenbroek, Ruth E., Idzerda, Rejean L., Scheuer, Todd, Scott, John D., Catterall, William A., McKnight, G. Stanley
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 30.09.1997; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences of the USA
• Subjects: Amino acids; Animals; Antibodies; Biochemistry; Biological Sciences; Calcium Channels - metabolism; Calcium Channels - physiology; Calcium Channels, L-Type; Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; Cyclic AMP-Dependent Protein Kinase Type II; Cyclic AMP-Dependent Protein Kinases - chemistry; Cyclic AMP-Dependent Protein Kinases - genetics; Cyclic AMP-Dependent Protein Kinases - metabolism; Depolarization; Ion Channel Gating; Knockout mice; Mice; Mice, Knockout; Muscle fibers; Muscle, Skeletal - enzymology; Muscle, Skeletal - physiology; Muscles; Phosphorylation; Proteins; Skeletal muscle; Surface plasmon resonance
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.94.20.11067

Preferential phosphorylation of specific proteins by cAMP-dependent protein kinase (PKA) may be mediated in part by the anchoring of PKA to a family of A-kinase anchor proteins (AKAPs) positioned in close proximity to target proteins. This interaction is thought to depend on binding of the type II regulatory (RII) subunits to AKAPs and is essential for PKA-dependent modulation of the α -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate receptor, the L-type Ca2+channel, and the KCachannel. We hypothesized that the targeted disruption of the gene for the ubiquitously expressed RIIα subunit would reveal those tissues and signaling events that require anchored PKA. RIIα knockout mice appear normal and healthy. In adult skeletal muscle, RIα protein levels increased to partially compensate for the loss of RIIα . Nonetheless, a reduction in both catalytic (C) subunit protein levels and total kinase activity was observed. Surprisingly, the anchored PKA-dependent potentiation of the L-type Ca2+channel in RIIα knockout skeletal muscle was unchanged compared with wild type although it was more sensitive to inhibitors of PKA-AKAP interactions. The C subunit colocalized with the L-type Ca2+channel in transverse tubules in wild-type skeletal muscle and retained this localization in knockout muscle. The RIα subunit was shown to bind AKAPs, although with a 500-fold lower affinity than the RIα subunit. The potentiation of the L-type Ca2+channel in RIIα knockout mouse skeletal muscle suggests that, despite a lower affinity for AKAP binding, RIα is capable of physiologically relevant anchoring interactions.