Disease relevance of AKAP1

• Gravin staining is coincident with an AKAP detected by an in situ RII-overlay assay, and a PKA-gravin complex can be isolated from human erythroleukemia cells [1].
• RESULTS: We have identified and characterized another mammalian scaffold protein which coordinates the location of protein kinase A and protein kinase C. We isolated a cDNA encoding a 250 kDa A-skinase anchoring protein (AKAP) called gravin, which was originally identified as a cytoplasmic antigen recognized by myasthenia gravis sera [1].
• PKA/AKAP/VR-1 module: A common link of Gs-mediated signaling to thermal hyperalgesia [2].

High impact information on AKAP1

• These methods use FRET probes based upon either protein kinase A (PKA) or EPAC, cAMP-gated ion channels, or the selective activation of AKAP-anchored PKA isoforms [3].
• AKAP mediated signal transduction [4].
• Thus, the PKA-mediated regulation of L-type Ca2+ channels is critically dependent on a functional AKAP and phosphorylation of the alpha1C subunit at Ser1928 [5].
• Furthermore, we have demonstrated that the association of an AKAP with PKA was required for beta-adrenergic receptor-mediated regulation of L-type channels in native cardiac myocytes, illustrating that the events observed in the heterologous expression system reflect those occurring in the native system [5].
• The PKA, PKC, and protein phosphatase-2B/calcineurin (CaN) scaffold protein A-kinase anchoring protein (AKAP) 79 is localized to excitatory neuronal synapses where it is recruited to glutamate receptors by interactions with membrane-associated guanylate kinase (MAGUK) scaffold proteins [6].

Biological context of AKAP1

• It was also found that the formation of the complex of AMY-1 with AKAP84/95 and RII prevented a catalytic subunit from binding to this AKAP complex, leading to suppression of PKA activity [7].
• AMY-1 was also found to be associated with protein kinase A anchor protein 84/149 (S-AKAP84/AKAP149) in the mitochondria in somatic cells and sperm, suggesting that it plays a role in spermatogenesis [8].
• The 3.2-kilobase S-AKAP84 mRNA and the cognate S-AKAP84 RII binding protein are expressed principally in the male germ cell lineage [9].
• We propose that kinase and phosphatase anchoring at the NE by AKAP149 plays in a role in modulating nuclear reassembly at the end of mitosis [10].
• In vivo dissociation of PP1 from NE-bound AKAP149 in G1-phase nuclei triggers phosphorylation and depolymerization of A- and B-type lamins [11].

Anatomical context of AKAP1

• AMY-1 was expressed postmeiotically in the testis, as S-AKAP84 was expressed [12].
• Residues 1-30 at the NH2 terminus of S-AKAP84 constitute a putative signal/anchor sequence that may target the protein to the outer mitochondrial membrane [9].
• Characterization of S-AKAP84, a novel developmentally regulated A kinase anchor protein of male germ cells [9].
• The timing of S-AKAP84 expression is correlated with the de novo accumulation of RII alpha and RII beta subunits and the migration of mitochondria from the cytoplasm (round spermatids) to the cytoskeleton (midpiece in elongating spermatids) [9].
• Immunofluorescence analysis demonstrated that S-AKAP84 is co-localized with mitochondria in the flagellum [9].

Associations of AKAP1 with chemical compounds

• Dual specificity AKAP1, (D-AKAP1) binds to both type I and type II regulatory subunits and has two NH2-terminal (N0 and N1) and two COOH-terminal (C1 and C2) splice variants (. J. Biol. Chem. 272:8057) [13].
• Selective siRNA-mediated knockdown identifies AKAP79, which is constitutively associated with the beta2-AR, rather than isoprenaline-recruited gravin, as being the functionally relevant AKAP in this process [14].
• Thus, AKAP 121/149 contains a KH region that is essential to the translation inhibition of LPL in response to epinephrine [15].
• PI 3-kinase inhibition results in an increase in intracellular cAMP levels and in tyrosine phosphorylation of the protein kinase A-anchoring protein AKAP3 [16].
• Peptides with S151 or S159 as the only wt serine residue trigger dissociation of PP1 from immunoprecipitated AKAP149, whereas S151/159D mutants are ineffective [17].

Physical interactions of AKAP1

• Competition with a peptide covering the RII-binding domain of AKAP Ht31 abolished RIIalpha binding to AKAP95 [18].
• Purified AKAP121 KH domain binds the 3' untranslated regions (3'UTRs) of transcripts encoding the Fo-f subunit of mitochondrial ATP synthase and manganese superoxide dismutase (MnSOD) [19].

Other interactions of AKAP1

• We show that both AKAP79 and S-AKAP84/D-AKAP1 bind RIIalpha very well (apparent K(D) values of 0.5 and 2 nM, respectively) [20].
• Analysis of A-kinase anchoring protein (AKAP) interaction with protein kinase A (PKA) regulatory subunits: PKA isoform specificity in AKAP binding [20].
• Protein kinase A-anchoring (AKAP) domains in brefeldin A-inhibited guanine nucleotide-exchange protein 2 (BIG2) [21].
• Immunoprecipitation of Jurkat cell lysates with Abs against both the regulatory subunit of PKA (RIIalpha) and specific AKAPs resulted in increased PDE activity associated with RIIalpha and AKAP95, AKAP149, and myeloid translocation gene (MTG) compared with control (IgG) [22].
• Screening of a PMA-stimulated Jurkat cell library identified two additional known AKAPs, AKAP220 and AKAP-KL, and one novel AKAP, myeloid translocation gene 16 (MTG16b) [23].

Analytical, diagnostic and therapeutic context of AKAP1

• Western blot analyses identified four known AKAPs: AKAP79, AKAP95, AKAP149, and WAVE [23].
• We have now purified the 78 kDa AKAP to homogeneity from gastric fundic mucosal supernates using type II A-kinase regulatory subunit (RII) affinity chromatography [24].
• Using a combination of protein kinase A type II overlay screening, rapid amplification of cDNA ends, and database searches, a contig of 9923 bp was assembled and characterized in which the open reading frame encoded a 1901-amino-acid A-kinase-anchoring protein (AKAP) with an apparent SDS-PAGE mobility of 220 kDa, named human AKAP220 (hAKAP220) [25].
• Immunoblotting analysis and trypsin digestion pattern show that 90% or more of mitochondrial C-PKA, R-PKA and AKAP121 is localized in the inner mitochondrial compartment, when prepared both from isolated mitochondria or cardiomyocyte cultures [26].
• This localization is verified by measurement of the specific catalytic activity of PKA, radiolabelling of R-PKA by (32)P-phosphorylated C-PKA and of AKAP by (32)P-phosphorylated R-PKA and electron microscopy of mitochondria exposed to gold-conjugated AKAP121 antibody [26].

References