4wbb | pdb_00004wbb
Single Turnover Autophosphorylation Cycle of the PKA RIIb Holoenzyme
Structural highlights
Function[KAP3_MOUSE] Regulatory subunit of the cAMP-dependent protein kinases involved in cAMP signaling in cells. Type II regulatory chains mediate membrane association by binding to anchoring proteins, including the MAP2 kinase. [KAPCA_MOUSE] Phosphorylates a large number of substrates in the cytoplasm and the nucleus. Regulates the abundance of compartmentalized pools of its regulatory subunits through phosphorylation of PJA2 which binds and ubiquitinates these subunits, leading to their subsequent proteolysis. Phosphorylates CDC25B, ABL1, NFKB1, CLDN3, PSMC5/RPT6, PJA2, RYR2, RORA, TRPC1 and VASP. RORA is activated by phosphorylation. Required for glucose-mediated adipogenic differentiation increase and osteogenic differentiation inhibition from osteoblasts. Involved in the regulation of platelets in response to thrombin and collagen; maintains circulating platelets in a resting state by phosphorylating proteins in numerous platelet inhibitory pathways when in complex with NF-kappa-B (NFKB1 and NFKB2) and I-kappa-B-alpha (NFKBIA), but thrombin and collagen disrupt these complexes and free active PRKACA stimulates platelets and leads to platelet aggregation by phosphorylating VASP. Prevents the antiproliferative and anti-invasive effects of alpha-difluoromethylornithine in breast cancer cells when activated. RYR2 channel activity is potentiated by phosphorylation in presence of luminal Ca(2+), leading to reduced amplitude and increased frequency of store overload-induced Ca(2+) release (SOICR) characterized by an increased rate of Ca(2+) release and propagation velocity of spontaneous Ca(2+) waves, despite reduced wave amplitude and resting cytosolic Ca(2+). TRPC1 activation by phosphorylation promotes Ca(2+) influx, essential for the increase in permeability induced by thrombin in confluent endothelial monolayers. PSMC5/RPT6 activation by phosphorylation stimulates proteasome. Regulates negatively tight junction (TJs) in ovarian cancer cells via CLDN3 phosphorylation. NFKB1 phosphorylation promotes NF-kappa-B p50-p50 DNA binding. Involved in embryonic development by down-regulating the Hedgehog (Hh) signaling pathway that determines embryo pattern formation and morphogenesis. Isoform 2 phosphorylates and activates ABL1 in sperm flagellum to promote spermatozoa capacitation. Prevents meiosis resumption in prophase-arrested oocytes via CDC25B inactivation by phosphorylation. May also regulate rapid eye movement (REM) sleep in the pedunculopontine tegmental (PPT).[1] [2] [3] Publication Abstract from PubMedTo provide tight spatiotemporal signaling control, the cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) holoenzyme typically nucleates a macromolecular complex or a "PKA signalosome." Using the RIIbeta holoenzyme as a prototype, we show how autophosphorylation/dephosphorylation of the RIIbeta subunit, as well as cAMP and metal ions, contribute to the dynamics of PKA signaling. While we showed previously that the RIIbeta holoenzyme could undergo a single turnover autophosphorylation with adenosine triphosphate and magnesium (MgATP) and trap both products in the crystal lattice, we asked here whether calcium could trap an ATP:RIIbeta holoenzyme since the RIIbeta holoenzyme is located close to ion channels. The 2.8A structure of an RIIbetap2:C2:(Ca2ADP)2 holoenzyme, supported by biochemical and biophysical data, reveals a trapped single phosphorylation event similar to MgATP. Thus, calcium can mediate a single turnover event with either ATP or adenosine-5'-(beta,gamma-imido)triphosphate (AMP-PNP), even though it cannot support steady-state catalysis efficiently. The holoenzyme serves as a "product trap" because of the slow off-rate of the pRIIbeta subunit, which is controlled by cAMP, not by phosphorylation of the inhibitor site. By quantitatively defining the RIIbeta signaling cycle, we show that release of pRIIbeta in the presence of cAMP is reduced by calcium, whereas autophosphorylation at the phosphorylation site (P-site) inhibits holoenzyme reassociation with the catalytic subunit. Adding a single phosphoryl group to the preformed RIIbeta holoenzyme thus creates a signaling cycle in which phosphatases become an essential partner. This previously unappreciated molecular mechanism is an integral part of PKA signaling for type II holoenzymes. Single Turnover Autophosphorylation Cycle of the PKA RIIbeta Holoenzyme.,Zhang P, Knape MJ, Ahuja LG, Keshwani MM, King CC, Sastri M, Herberg FW, Taylor SS PLoS Biol. 2015 Jul 9;13(7):e1002192. doi: 10.1371/journal.pbio.1002192., eCollection 2015 Jul. PMID:26158466[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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