Expression and Intracellular Localization of Protein Phosphatases 2A and 2B, Protein Kinase A, A-Kinase Anchoring Protein (AKAP79), and Binding of the Regulatory (RII) Subunit of Protein Kinase A to AKAP79 in Human Myometrium

Ayres, Allen; Carr, Daniel W.; McConnell, Daniel S.; Lieberman, Richard W.; Smith, Gary D.

doi:10.1016/s1071-55760300136-9

Cited by 6 publications

(4 citation statements)

References 38 publications

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“…The molecular weight estimation by SDS PAGE of approximately 44 kDa for PKAα Cat is the same reported by the antibody manufacturer when detecting PKAα Cat in mouse brain extract ( ) and similar to the estimated molecular weight of PKAα Cat previously found in the cytoplasm of human myometrium (approximately 42 kDa) [ 8 ]. SDS PAGE has an accuracy in molecular weight determination of up to approximately +/- 10% [ 26 ].…”

Section: Discussionsupporting

confidence: 83%

“…There are several forms of AKAP (often differentiated by a suffix corresponding to their molecular weight) that have been found in tissues and species other than placenta and human. The only form of AKAP found in human reproductive tissue prior to this investigation was AKAP79 which, was shown to be present in the cytoplasm of human myometrium and is thought to anchor PKA to the myometrial plasma membrane [ 8 ].…”

Section: Introductionmentioning

confidence: 99%

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Protein Kinase A Subunit α Catalytic and A Kinase Anchoring Protein 79 in Human Placental Mitochondria

Pui

Thomson

2012

TOBIOCJ

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Components of protein phosphorylation signalling systems have been discovered in mitochondria and it has been proposed that these molecules modulate processes including oxidative phosphorylation, apoptosis and steroidogenesis. We used electrophoresis and Western blots probed with specific antibodies to protein kinase A α catalytic subunit (PKAα Cat) and A kinase anchoring protein of approximately 79 kDa molecular weight (AKAP79) to demonstrate the presence of these two proteins in human placental mitochondria. Heavy mitochondria characteristic of cytotrophoblast were separated from light mitochondria characteristic of syncytiotrophoblast by centrifugation. PKAα Cat and AKAP79 were present in both heavy and light mitochondria with no significant difference in concentration. Sucrose density gradient separation of submitochondrial fractions indicated PKAα Cat is located predominantly in the outer membrane whereas AKAP79 is present mainly in the contact site fractions. These data indicate that PKAα Cat is present in the cytoplasm, nucleus and mitochondria of placental cells. AKAP79 is also present in human placental mitochondria but there may be anchoring proteins other than AKAP79 responsible for fixing PKA to the outer membrane. PKA may play roles in mitochondrial protein phosphorylation systems in both cytotrophoblast and syncytiotrophoblast.

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Protein Kinase A Subunit α Catalytic and A Kinase Anchoring Protein 79 in Human Placental Mitochondria

Pui

Thomson

2012

TOBIOCJ

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“…Progesterone treatment to postpone labor prevented the decline of membrane PKA 5. Data in humans also support a decline in plasma membrane‐associated PKA, as well as transcriptional downregulation of PKA, between not‐in‐labor and in‐labor samples 6,7. These data indicate that PKA acts as a functional counteragent to myometrium contraction.…”

Section: Crosstalk Exists Between Contractant‐ and Relaxant‐stimulatementioning

confidence: 64%

Pathways Used by Relaxin to Regulate Myometrial Phospholipase C

Zhong

Sanborn

2005

Annals of the New York Academy of Sciences

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Relaxin exhibits pleiotropic effects on reproductive and nonreproductive tissues; the signaling mechanisms underlying these functions are still not well understood. Activation of protein kinase A and several other signal-regulated protein kinases results in the phosphorylation of phospholipase C (PLC)-beta3 and inhibit Galpha(q)-stimulated PLC activity. Therefore, PLCbeta3 may be targeted by both contractant and relaxant signaling pathways in myometrium and play a critical role in the balance between them. PHM1 cells express mRNA for relaxin receptor LGR7, and relaxin inhibits oxytocin-stimulated PLC activity in these cells. Thus, this model system may be useful in delineating signaling pathways used by relaxin. Here, we present evidence that relaxin stimulates phosphorylation of PLCbeta3 in PHM1 cells.

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“…) and may play a similar role in the myometrium (Ayres et al . ). Another possible explanation for the decline in HSP20 Ser16‐phosphorylation may be attributed to 8‐bromo‐cAMP being able to activate PKG when used at high concentrations (as discussed above) and thus negative feedback on HSP20 Ser16‐phosphorylation may have originated from the prolonged activation of PKG instead of altered PKA activity; the same possibility could also apply to the loss of HSP20 Ser16‐phosphorylation following prolonged exposure to 6‐Bnz‐cAMP.…”

Section: Discussionmentioning

confidence: 97%

Differential impact of acute and prolonged cAMP agonist exposure on protein kinase A activation and human myometrium contractile activity

Lai

Tribe

Johnson

2016

The Journal of Physiology

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KEY POINTS SUMMARY Over 15 million babies are born prematurely each year with approximately 1 million of these babies dying as a direct result of preterm delivery. β 2 -adrenoreceptor agonists that act via cAMP can reduce uterine contractions to delay preterm labour, but their ability to repress uterine contractions lasts ≤ 48 hours and their use does not improve neonatal outcomes. Previous research has suggested that cAMP inhibits myometrial contractions via protein kinase A (PKA) activation, but this has yet to be demonstrated with PKA-specific agonists. We investigated the role of PKA in mediating cAMP-induced human myometrial relaxation, and the impact of prolonged cAMP elevation on myometrial contractility. Our findings suggest that PKA is not the sole mediator of cAMP-induced myometrial relaxation and that prolonged prophylactic elevation of cAMP alone is unlikely to prevent preterm labour (PTL). ABSTRACTAcute cAMP elevation inhibits myometrial contractility, but the mechanisms responsible are not fully defined and the long-term effects uncertain. These need to be defined in pregnant human myometrium before the therapeutic potential of cAMP-elevating agents in the prevention of preterm labour can be realised. In the present study, we tested the hypotheses that PKA activity is necessary for cAMP-induced myometrial relaxation and prolonged cAMP elevation can prevent myometrial contractions. Myometrial tissues obtained from term, pre-labour elective Caesarean sections were exposed to receptor-independent cAMP agonists to determine the relationship between myometrial contractility (spontaneous and oxytocin-induced), PKA activity, HSP20 phosphorylation and expression of contractionassociated and cAMP signalling proteins. Acute (1 h) application of cAMP agonists This article is protected by copyright. All rights reserved. 3promoted myometrial relaxation but this was weakly related to PKA activation. PKA-specific activator, 6-Bnz-cAMP, increased PKA activity (6.8 ± 2.0 mean fold versus vehicle; p = 0.0313) without inducing myometrial relaxation. Spontaneous myometrial contractility declined after 24 hours but was less marked when tissues were constantly exposed to cAMP agonists, especially for 8-bromo-cAMP (4.3 ± 1.2 mean fold versus vehicle; p = 0.0043); this was associated with changes to calponin, cofilin and HSP20 phosphorylated/total protein levels. Oxytocin-induced contractions were unaffected by pre-incubation with cAMP agonists despite treatments being able to enhance PKA activity and HSP20 phosphorylation. These data suggest that cAMP-induced myometrial relaxation is not solely dependent on PKA activity and the ability of cAMP agonists to repress myometrial contractility is lost with prolonged exposure. We conclude that cAMP agonist treatment alone may not prevent preterm labour.

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Expression and Intracellular Localization of Protein Phosphatases 2A and 2B, Protein Kinase A, A-Kinase Anchoring Protein (AKAP79), and Binding of the Regulatory (RII) Subunit of Protein Kinase A to AKAP79 in Human Myometrium

Cited by 6 publications

References 38 publications

Protein Kinase A Subunit α Catalytic and A Kinase Anchoring Protein 79 in Human Placental Mitochondria

Protein Kinase A Subunit α Catalytic and A Kinase Anchoring Protein 79 in Human Placental Mitochondria

Pathways Used by Relaxin to Regulate Myometrial Phospholipase C

Differential impact of acute and prolonged cAMP agonist exposure on protein kinase A activation and human myometrium contractile activity

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