Evolution of the cAMP-dependent protein kinase (PKA) catalytic subunit isoforms

Søberg, Kristoffer; Moen, Line Victoria; Skålhegg, Bjørn Steen; Laerdahl, Jon K.

doi:10.1371/journal.pone.0181091

Cited by 40 publications

(43 citation statements)

References 67 publications

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“…The oncogenic J-PKAcα has been crystallized here for the first time in one of its most important physiological states where it is associated in a holoenzyme complex with the RIα subunit. This structure demonstrates that the N-terminal fusion does not interfere with the general organization of the R 2 :PKAcα 2 holoenzyme, and this also has relevance for the various PKAcα isoforms some of which have large extensions at the N-terminus (Søberg et al, 2017). Comparing the conformational states of the wt and chimeric RIα holoenzymes that display some novel interfaces may guide the development of drugs that selectively target not only to the J-domain and catalytic core to directly block chimera activity, but also regions present only at the holoenzyme level to block holoenzyme activation.…”

Section: Discussionmentioning

confidence: 83%

Structures of the PKA RIα holoenzyme with the FLHCC driver J-PKAcα or wild type PKAcα

Cao

Fiesco

et al. 2018

Preprint

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1Fibrolamellar hepatocellular carcinoma (FLHCC) is driven by J-PKAcα, a kinase fusion chimera 2 2 of the J-domain of DnaJB1 with PKAcα, the catalytic subunit of Protein Kinase A (PKA). Here 2 3 we report the crystal structures of the chimeric fusion RIα 2 :J-PKAcα 2 holoenzyme formed by J-2 4 PKAcα and the PKA regulatory (R) subunit RIα, and the wild type (wt) RIα 2 :PKAcα 2 2 5 holoenzyme. The chimeric and wt RIα holoenzymes have quaternary structures different from 2 6 the previously solved wt RIβ and RIIβ holoenzymes. The chimeric holoenzyme shows an 2 7isoform-specific interface dominated by antiparallel interactions between the N3A-N3A' motifs 2 8of RIα that serves as an anchor for RIα structural rearrangements during cAMP activation. The 2 9wt RIα holoenzyme showed the same configuration as well as a distinct second conformation. In 3 0 the structure of the chimeric fusion RIα 2 :J-PKAcα 2 holoenzyme, the presence of the J-domain 3 1 does not prevent formation of the holoenzymes, and is positioned away from the symmetrical 3 2 interface between the two RIα:J-PKAcα heterodimers in the holoenzyme. The J-domains have 3 3 significantly higher temperature factors than the rest of the holoenzyme, implying a large degree 3 4 of conformational flexibility. Furthermore molecular dynamics simulations were applied to 3 5 analyze the conformational states of chimeric fusion and wt RIα holoenzymes, and showed an 3 6 ensemble of conformations in the majority of which the J-domain was dynamic and rotated away 3 7 from the R:J-PKAcα interface. Thus, rather than affecting the interactions with the regulatory 3 8 subunits, the fusion of the J-domain to the PKAcα alters the conformational landscape of the 3 9 chimeric fusion holoenzymes and potentially, as result, the interactions with other molecules.4 0The structural and dynamic features of these holoenzymes enhance our understanding of the 4 1 fusion chimera protein J-PKAcα that drives FLHCC as well as the isoform specificity of PKA. 4 2 4 3

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Section: Discussionmentioning

confidence: 83%

Structures of the PKA RIα holoenzyme with the FLHCC driver J-PKAcα or wild type PKAcα

Cao

Fiesco

et al. 2018

Preprint

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“…of the sperm form of the enzyme with the somatic form of the PKA catalytic subunit would sustain normal sperm function is not known. However, it is intriguing that exon 1b, the sperm specific isoform of PKA, is present only in mammals (Soberg et al, 2017). Non-mammalian species only contain the isoform derived from utilization of exon 1a ( Figure 4B).…”

Section: The Proteins Pp1γ2 Gsk3α Pka Cα2 and Ppp3r2/cc Present Onmentioning

confidence: 99%

Signaling Enzymes Required for Sperm Maturation and Fertilization in Mammals

Dey

Brothag

Vijayaraghavan

2019

Front. Cell Dev. Biol.

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In mammals, motility and fertilizing ability of spermatozoa develop during their passage through the epididymis. After ejaculation, sperm undergo capacitation and hyperactivation in the female reproductive tract-a motility transition that is required for sperm penetration of the egg. Both epididymal initiation of sperm motility and hyperactivation are essential for male fertility. Motility initiation in the epididymis and sperm hyperactivation involve changes in metabolism, cAMP (cyclic adenosine monophosphate), calcium and pH acting through protein kinases and phosphatases. Despite this knowledge, we still do not understand, in biochemical terms, how sperm acquire motility in the epididymis and how motility is altered in the female reproductive tract. Recent data show that the sperm specific protein phosphatase PP1γ2, glycogen synthase kinase 3 (GSK3), and the calcium regulated phosphatase calcineurin (PP2B), are involved in epididymal sperm maturation. The protein phosphatase PP1γ2 is present only in testis and sperm in mammals. PP1γ2 has a isoform-specific requirement for normal function of mammalian sperm. Sperm PP1γ2 is regulated by three proteinsinhibitor 2, inhibitor 3 and SDS22. Changes in phosphorylation of these three inhibitors and their binding to PP1γ2 are involved in initiation and activation of sperm motility. The inhibitors are phosphorylated by protein kinases, one of which is GSK3. The isoform GSK3α is essential for epididymal sperm maturation and fertility. Calcium levels dramatically decrease during sperm maturation and initiation of motility suggesting that the calcium activated sperm phosphatase (PP2B) activity also decreases. Loss of PP2B results in male infertility due to impaired sperm maturation in the epididymis. Thus the three signaling enzymes PP1γ2, GSK3, and PP2B along with the documented PKA (protein kinase A) have key roles in sperm maturation and hyperactivation. Significantly, all these four signaling enzymes are present as specific isoforms only in placental mammals, a testimony to their essential roles in the unique aspects of sperm function in mammals. These findings should lead to a better biochemical understanding of the basis of male infertility and should lead to novel approaches to a male contraception and managed reproduction.

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“…Recently we performed alignments of exon 1-1 encoded Cα1/Cβ1 across species after the gene duplication yielding Cα and Cβ isoforms, and pre-duplication catalytic subunit [designated C1, ( 188 )] residues reveals several conserved features in the N-terminus during evolution of the C subunit. Out of all 15 positions, position 1 and 2 is invariably Gly1 and Asn2 in both Cα1 and Cβ1, as well as C1, an ancient form of Cα and Cβ.…”

Section: Structural Relationships Of the N-terminal End Of The C Subumentioning

confidence: 99%

“…It is well-established that Gly1 may have a function in mammals through its modification of myristoylation by the enzyme NMT ( 74 ). We have suggested that N-myristoylation of PKA C subunits is a feature found in all vertebrate Cα1/Cβ1 subunits, and maybe even all metazoan C1 subunits in general ( 188 ). N-terminal myristoylation of proteins appears to be an ancient mechanism, with the common ancestor gene of NMT possibly arising in early eukaryotic cells ( 189 ).…”

Section: Structural Relationships Of the N-terminal End Of The C Subumentioning

confidence: 99%

“…The β-Aspartyl shift mechanism ( 83 ), i.e., deamidation of Asn into Asp, occurs especially in the case of Asn being followed by residues Gly, Ser, or Ala ( 82 ). Indeed, alignment reveals that position 3 of vertebrate Cα1/Cβ1 subunits is either Ser, Ala, or Thr ( 188 ). Whether the rate of deamidation of Asn2 of isoforms such as Cβ1 of mouse, containing Thr3, is reduced (and as a consequence reduced phosphorylation of Ser10) has not been determined.…”

Section: Structural Relationships Of the N-terminal End Of The C Subumentioning

confidence: 99%

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The Molecular Basis for Specificity at the Level of the Protein Kinase a Catalytic Subunit

Søberg

Skålhegg

2018

Front. Endocrinol.

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Assembly of multi enzyme complexes at subcellular localizations by anchoring- and scaffolding proteins represents a pivotal mechanism for achieving spatiotemporal regulation of cellular signaling after hormone receptor targeting [for review, see (1)]. In the 3′ 5′-cyclic adenosine monophosphate (cAMP) dependent protein kinase (PKA) signaling pathway it is generally accepted that specificity is secured at several levels. This includes at the first level stimulation of receptors coupled to heterotrimeric G proteins which through stimulation of adenylyl cyclase (AC) forms the second messenger cAMP. Cyclic AMP has several receptors including PKA. PKA is a tetrameric holoenzyme consisting of a regulatory (R) subunit dimer and two catalytic (C) subunits. The R subunit is the receptor for cAMP and compartmentalizes cAMP signals through binding to cell and tissue-specifically expressed A kinase anchoring proteins (AKAPs). The current dogma tells that in the presence of cAMP, PKA dissociates into an R subunit dimer and two C subunits which are free to phosphorylate relevant substrates in the cytosol and nucleus. The release of the C subunit has raised the question how specificity of the cAMP and PKA signaling pathway is maintained when the C subunit no longer is attached to the R subunit-AKAP complex. An increasing body of evidence points toward a regulatory role of the cAMP and PKA signaling pathway by targeting the C subunits to various C subunit binding proteins in the cytosol and nucleus. Moreover, recent identification of isoform specific amino acid sequences, motifs and three dimensional structures have together provided new insight into how PKA at the level of the C subunit may act in a highly isoform-specific fashion. Here we discuss recent understanding of specificity of the cAMP and PKA signaling pathway based on C subunit subcellular targeting as well as evolution of the C subunit structure that may contribute to the dynamic regulation of C subunit activity.

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Evolution of the cAMP-dependent protein kinase (PKA) catalytic subunit isoforms

Cited by 40 publications

References 67 publications

Structures of the PKA RIα holoenzyme with the FLHCC driver J-PKAcα or wild type PKAcα

Structures of the PKA RIα holoenzyme with the FLHCC driver J-PKAcα or wild type PKAcα

Signaling Enzymes Required for Sperm Maturation and Fertilization in Mammals

The Molecular Basis for Specificity at the Level of the Protein Kinase a Catalytic Subunit

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