mTOR Kinase and the Regulatory Subunit of Protein Kinase A (PRKAR1A) Spatially and Functionally Interact during Autophagosome Maturation

Most PRKAR1A tumorigenic mutations lead to nonsense mRNA that is decayed; tumor formation has been associated with an increase in type II protein kinase A (PKA) subunits. The IVS6+1G>T PRKAR1A mutation leads to a protein lacking exon 6 sequences [R1A#184-236 (R1A#6)]. We compared in vitro R1A#6 with wild-type (wt) R1A. We assessed PKA activity and subunit expression, phosphorylation of target molecules, and properties of wt-R1A and mutant (mt) R1A; we observed by confocal microscopy R1A tagged with green fluorescent protein and its interactions with Cerulean-tagged catalytic subunit (CA). Introduction of the R1A#6 led to aberrant cellular morphology and higher PKA activity but no increase in type II PKA subunits. There was diffuse, cytoplasmic localization of R1A protein in wt-R1A-and R1A#6-transfected cells but the former also exhibited discrete aggregates of R1A that bound CA; these were absent in R1A#6-transfected cells and did not bind CA at baseline or in response to cyclic AMP. Other changes induced by R1A#6 included decreased nuclear CA. We conclude that R1A#6 leads to increased PKA activity through the mt-R1A decreased binding to CA and does not involve changes in other PKA subunits, suggesting that a switch to type II PKA activity is not necessary for increased kinase activity or tumorigenesis. [Cancer Res 2008;68(9):3133-41]

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“…GFP tagged to the NH 2 or the COOH terminus of R1a resulted in similar formations (17,30), and R1aD6-GFP completely lacked them (Fig. 6A).…”

Section: Discussionmentioning

confidence: 99%

“…Several other findings are worthy of discussion, however, and require further investigation: Wt-R1a formed cytosolic aggregates, puncta, that have been seen by us (17,30) and by other investigators and in various (although not all) types of cells, tagged with GFP (17,30,31) and untagged (32,33). Zaccolo et al (34) Figure 6.…”

Section: Discussionmentioning

confidence: 99%

Protein Kinase A Effects of an Expressed PRKAR1A Mutation Associated with Aggressive Tumors

et al. 2008

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“…Recent evidence supports intracellular localization of mTOR at the endosomes (62)(63)(64)(65). Whether Smad 3 binds mTOR in TGF␤-stimulated cells is not known.…”

Section: Discussionmentioning

confidence: 99%

Transforming Growth Factor β Integrates Smad 3 to Mechanistic Target of Rapamycin Complexes to Arrest Deptor Abundance for Glomerular Mesangial Cell Hypertrophy

Das

Ghosh‐Choudhury

Bera

et al. 2013

Journal of Biological Chemistry

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Background: Transforming growth factor ␤ (TGF␤) induces renal hypertrophy and fibrosis. Results: TGF␤-induced deptor down-regulation is necessary for prolonged activation of TORC1/2 and mesangial cell hypertrophy. Conclusion: TGF␤-stimulated Smad 3 contributes to deptor suppression and mammalian target of rapamycin activation. Significance: Sustained deptor expression may alleviate renal glomerular hypertrophy and fibrosis.

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“…The RIα subunit of PKA was found to localize on Rab7-positive late endosomes and on microtubule-associated protein light chain 3-positive autophagosomes in cultured cells. RIα was also shown to physically interact with the mTOR (mammalian target of rapamycin) kinase and affect its phosphorylation and activity (94) . While the regulation of autophagocytosis by cAMP levels is highly conditional (95) , .…”

Section: The Role Of Camp/pka In Endocytosismentioning

confidence: 99%

cAMP‐dependent protein kinase A and the dynamics of epithelial cell surface domains: Moving membranes to keep in shape

2008

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mTOR Kinase and the Regulatory Subunit of Protein Kinase A (PRKAR1A) Spatially and Functionally Interact during Autophagosome Maturation

Cited by 33 publications

References 13 publications

Protein Kinase A Effects of an Expressed PRKAR1A Mutation Associated with Aggressive Tumors

Protein Kinase A Effects of an Expressed PRKAR1A Mutation Associated with Aggressive Tumors

Transforming Growth Factor β Integrates Smad 3 to Mechanistic Target of Rapamycin Complexes to Arrest Deptor Abundance for Glomerular Mesangial Cell Hypertrophy

cAMP‐dependent protein kinase A and the dynamics of epithelial cell surface domains: Moving membranes to keep in shape

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