α4 Integrins are Type I cAMP-dependent protein kinase-anchoring proteins

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Abstract
A-kinase anchoring proteins (AKAPs) control the localization and substrate specificity of cAMP-dependent protein kinase (PKA), tetramers of regulatory (PKA-R) and catalytic (PKA-C) subunits, by binding to PKA-R subunits1. Most mammalian AKAPs bind Type II PKA through PKA-RII (ref. 2), whereas dual specificity AKAPs bind both PKA-RI and PKA-RII (ref. 3). Inhibition of PKA–AKAP interactions modulates PKA signalling2. Localized PKA activation in pseudopodia of migrating cells4 phosphorylates α4 integrins to provide spatial cues governing cell motility5. Here, we report that the α4 cytoplasmic domain is a Type I PKA-specific AKAP that is distinct from canonical AKAPs in two ways: the α4 interaction requires the PKA holoenzyme, and is insensitive to amphipathic peptides that disrupt most PKA–AKAP interactions. We exploited type-specific PKA anchoring peptides to create genetically encoded baits that sequester specific PKA isoforms to the mitochondria and found that mislocalization of Type I, but not Type II, PKA disrupts α4 phosphorylation and markedly inhibits the velocity and directional persistence of cell migration.