8uko
cAMP-dependent protein kinase A catalytic domain in complex with voltage gated calcium channel peptide ternary complex 2
Structural highlights
FunctionKAPCA_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 PubMedbeta-adrenergic signalling activates cAMP-dependent protein kinase (PKA), which regulates the activity of L-type voltage-gated calcium channels such as Ca(V)1.2. Several PKA target sites in the C-terminal tail of Ca(V)1.2 have been identified, and their phosphorylation has been suggested to increase currents in specific tissues or heterologous expression systems. However, augmentation of Ca(V)1.2 currents in the heart is instead mediated by phosphorylation of Rad, a small GTPase that can inhibit Ca(V)1.2. It is unclear how each of the proposed target sites in Ca(V)1.2 and Rad rank towards their recognition by PKA, which could reveal a preferential phosphorylation. Here we used quantitative assays on three Ca(V)1.2 and four Rad sites. Isothermal titration calorimetry (ITC) and enzyme kinetics show that there are two Tiers of targets, with Ca(V)1.2 residue Ser1981 and Rad residues Ser25 and Ser272 forming Tier 1 substrates for PKA. These share a common feature with two Arginine residues at specific positions that can anchor the peptide into the substrate binding cleft of PKA. In contrast, PKA shows minimal activity for the other, Tier 2 substrates, characterized by low k(cat) values and undetectable binding via ITC. The existence of two Tiers suggests that PKA regulation of the Ca(V)1.2 complex may occur in a graded fashion. We report crystal structures of the PKA catalytic subunit with and without a Ca(V)1.2 and test the importance of several anchoring residues via mutagenesis. Different target sites utilize different anchors, highlighting the plasticity of PKAc to recognize substrates. Crystallographic, kinetic, and calorimetric investigation of PKA interactions with L-type calcium channels and Rad GTPase.,Yoo R, Haji-Ghassemi O, Bader M, Xu J, McFarlane C, van Petegem F J Biol Chem. 2024 Nov 28:108039. doi: 10.1016/j.jbc.2024.108039. PMID:39615689[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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