Selective hormonal activation of cyclic AMP-dependent protein kinase isoenzymes in normal and malignant osteoblasts.

Livesey, Steven; Kemp, Bruce E.; Re, Catalán; Partridge, Nicola C.; Martin, T. J.

doi:10.1016/s0021-9258(18)33381-7

Cited by 108 publications

(5 citation statements)

References 27 publications

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“…Chromatographic analysis of the protein kinase holoenzymes remaining after hormonal stimulation indicated selective activation of the type I isoenzyme in a wide range of cells and tissues (Schwoch, 1978;Byus et al, 1977;Hunzicker-Dunn, 1981). Conflicting reports from one other group (Livesey et al, 1982;Livesey et al, 1984) may relate to the difficulties inherent in this type of analyses that cannot exclude reassociation and redistribution of subunits during preparation of extracts. Our data do not exclude additional factors modulating protein kinase activation.…”

Section: Discussionmentioning

confidence: 96%

cAMP-dependent protein kinases I and II: divergent turnover of subunits

Weber¹,

Hilz²

1986

Biochemistry

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cAMP-dependent protein kinase subunits were isolated from livers of rats that had been subjected to biosynthetic labeling with radioactive leucine. By application of ligand and antibody affinity techniques pure regulatory (R I; R II) and catalytic (C) subunits could be obtained in high yields, which allowed measurement of the apparent degradation rate constants and half-lives following a double isotope labeling protocol. In this way marked differences of apparent half-lives of regulatory subunits R I (t1/2 = 31 h) and R II (t1/2 = 125 h) were observed. To avoid the negative influence of reutilization inherent in the decay experiments, specific radioactivities were determined after a short isotope pulse. This parameter, which under steady-state conditions reflects the fractional turnover rate of the subunits, was found to be different for all three protein kinase subunits. Relative to total liver protein, the ratios R I:R II:C corresponded to 3.9:0.6:2. Our data indicate that in each type of protein kinase isoenzymes regulatory and catalytic subunits turn over with similar rates. The type I isoenzyme, however, is renewed much faster than protein kinase II. Furthermore, our findings are consistent with the thesis that free subunits as generated by activation are more susceptible to degradation than the holoenzymes, leading under steady-state conditions to compensatory resynthesis. Since renewal of R I exceeded that of R II also in two other tissues, the elevated turnover of protein kinase I as an indicator of preferential activation appears to be a general phenomenon. The different turnover of the two isoenzymes, then, may relate to different cellular functions like modulation of enzyme activity vs. modulation of gene activity.

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Section: Discussionmentioning

confidence: 96%

cAMP-dependent protein kinases I and II: divergent turnover of subunits

Weber¹,

Hilz²

1986

Biochemistry

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“…On the other hand, signaling read – outs in the case of PTH1R activation of the osteoblast lineage are seen much later, and intermediate steps of regulated gene expression are poorly defined. This was the case when these studies on activation of PKA were carried out ( 43 , 51 , 52 ), and it remains so today.…”

Section: Early Events In Camp and Protein Kinase A Activation In Osteoblastsmentioning

confidence: 94%

“…A notable feature seen with both PTH and PGE 2 was that PKA activation was a much more sensitive response than that of total cell cAMP concentration ( 43 ). Activation of PKA was rapid, reaching maximum within 30 to 60 secs, with readily demonstrable activation taking place even before increases in total cell cAMP could be detected ( 42 , 43 ). This is shown for PTH in osteogenic sarcoma cells and mouse calvarial osteoblasts ( Figure 2A ), with very similar data obtained with prostaglandin E 2 ( 43 ).…”

Section: Early Events In Camp and Protein Kinase A Activation In Osteoblastsmentioning

confidence: 99%

“…Activation of PKA was rapid, reaching maximum within 30 to 60 secs, with readily demonstrable activation taking place even before increases in total cell cAMP could be detected ( 42 , 43 ). This is shown for PTH in osteogenic sarcoma cells and mouse calvarial osteoblasts ( Figure 2A ), with very similar data obtained with prostaglandin E 2 ( 43 ). The data implied that only a fraction of the total amount of cAMP that can be generated by hormone stimulation is necessary to activate the protein kinase.…”

Section: Early Events In Camp and Protein Kinase A Activation In Osteoblastsmentioning

confidence: 99%

“…Development of chromatographic methods of separating and analysing the individual isoenzymes led to identification that PKA isoenzymes could be individually and independently activated by isoproterenol and PGE in guinea pig and rat heart ( 65 , 66 ). Modification of this approach to assess acute hormonal activation of each isoenzyme in cells in culture revealed that selective isoenzyme activation of individual isoenzymes I and II can occur in osteoblasts and osteosarcoma cells in response to PTH ( 43 , 67 ), as well as in human breast cancer cells T47D and MCF7 in response to calcitonin and PGE2 ( 68 ). The cells were intact when treated but needed to be disrupted for assays, with appropriate controls.…”

Section: Spatial Organization Of Molecular Eventsmentioning

confidence: 99%

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PTH1R Actions on Bone Using the cAMP/Protein Kinase A Pathway

Martın

2022

Front. Endocrinol.

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After the initial signaling action of parathyroid hormone (PTH) on bone was shown to be activation of adenylyl cyclase, its target was found to be cells of the osteoblast lineage, to the exclusion of osteoclasts and their precursors. This led to the view that the osteoblast lineage regulated osteoclast formation, a proposal that was established when the molecular mechanisms of osteoclast formation were discovered. This is in addition to the effect of PTH1Rv signaling throughout the osteoblast differentiation process to favour the formation of bone-forming osteoblasts. Initial signaling in the PTH target cells through cAMP and protein kinase A (PKA) activation is extremely rapid, and marked by an amplification process in which the later event, PKA activation, precedes cAMP accumulation in time and is achieved at lower concentrations. All of this is consistent with the existence of “spare receptors”, as is the case with several other peptide hormones. PTH-related protein (PTHrP), that was discovered as a cancer product, shares structural similarity with PTH in the amino-terminal domain that allows the hormone, PTH, and the autocrine/paracrine agent, PTHrP, to share actions upon a common G protein coupled receptor, PTH1R, through which they activate adenylyl cyclase with equivalent potencies. Studies of ligand-receptor kinetics have revealed that the PTH/PTH1R ligand-receptor complex, after initial binding and adenylyl cyclase activation at the plasma membrane, is translocated to the endosome, where adenylyl cyclase activation persists for a further short period. This behavior of the PTH1R resembles that of a number of hormones and other agonists that undergo such endosomal translocation. It remains to be determined whether and to what extent the cellular effects through the PTH1R might be influenced when endosomal is added to plasma membrane activation.

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Mechanisms by which Cyclic Nucleotides and Other Intracellular Mediators Regulate Secretion

Jonge¹,

Lohmannt

1985

Novartis Foundation Symposia

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Selective hormonal activation of cyclic AMP-dependent protein kinase isoenzymes in normal and malignant osteoblasts.

Cited by 108 publications

References 27 publications

cAMP-dependent protein kinases I and II: divergent turnover of subunits

cAMP-dependent protein kinases I and II: divergent turnover of subunits

PTH1R Actions on Bone Using the cAMP/Protein Kinase A Pathway

Mechanisms by which Cyclic Nucleotides and Other Intracellular Mediators Regulate Secretion

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