Secretagogue-induced proteolysis of cAMP-dependent protein kinase in intact rat alveolar epithelial type II cells

Zimmerman, Un‐Jin P.; Wang, Mengshu; Nelson, June; Ekwunife, Felix S.; Liu, Lin

doi:10.1016/0167-4889(95)00181-6

Cited by 17 publications

(7 citation statements)

References 23 publications

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“…reported to cleave and activate PKA (48). The mechanism by which HG activates PKA and potential involvement of calpain are exciting areas of future investigation.…”

Section: Discussionmentioning

confidence: 99%

Protein Kinase A-dependent Translocation of Hsp90α Impairs Endothelial Nitric-oxide Synthase Activity in High Glucose and Diabetes

Lei

Venkatakrishnan

et al. 2007

Journal of Biological Chemistry

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Diabetes mellitus (DM) and high glucose (HG) are known to reduce the bioavailability of nitric oxide (NO) by modulating endothelial nitric-oxide synthase (eNOS) activity. eNOS is regulated by several mechanisms including its interaction with heat shock protein (Hsp) 90. We previously discovered that DM in vivo and HG in vitro induced the translocation of Hsp90␣ to the outside of aortic endothelial cells. In this report we tested the hypothesis that translocation of Hsp90␣ is responsible for the decline in NO production observed in HG-treated cells. We found that HG increased phosphorylation of Hsp90␣ in a cAMP-dependent protein kinase A-dependent manner, and that this event was required for translocation of Hsp90␣ in porcine aortic endothelial cells. Furthermore, preventing translocation of Hsp90␣ protected from the HG-induced decline in eNOS⅐Hsp90␣ complex and NO production. Notably, DM increased phosphorylation of Hsp90␣ and reduced its association with eNOS in the aortic endothelium of diabetic rats. These studies suggest that translocation of Hsp90␣ is a novel mechanism by which HG and DM impair eNOS activity and thereby reduce NO production. Endothelium-derived nitric oxide (NO)2 , a small, diffusible, lipophilic free radical gas, is a critical regulator of cardiovascular homeostasis (1, 2). Vascular NO dilates all types of blood vessels. It also inhibits platelet aggregation and adhesion, and leukocyte adhesion to the vessel wall (3-5). A deficiency of NO (decreased NO production, increased degradation of NO or decreased NO sensitivity) can promote atherogenesis (1, 6).Endothelial NO synthase (eNOS) is responsible for most of the vascular NO produced. A functional eNOS oxidizes its substrate L-arginine to L-citrulline and NO (4, 5). eNOS is highly regulated by post-translational modifications including myristoylation, palmitoylation, and phosphorylation (7-11). This enzyme is also tightly regulated by specific interactions with inhibitory and activating proteins such as caveolin-1 and Hsp90, respectively. The binding of heat shock protein 90 (Hsp90) to eNOS enhances eNOS activation, assists with the intracellular trafficking of eNOS, and helps activate eNOS by dissociating it from caveolin-1 (12, 13). Furthermore, Hsp90 provides a scaffold for eNOS and Akt, and thereby enhances eNOS activation (9, 14 -16).Several studies have demonstrated that hyperglycemia/diabetes mellitus (DM) causes a loss of endothelium-derived NO in both animals (17-19) and humans (20), but the underlining mechanism is poorly understood. DM does not influence the overall eNOS protein level or its mRNA level (21). One potential mechanism may be the reduced association of eNOS with Hsp90 (19).Hsp90 is an ATP-dependent chaperone that interacts with over 100 proteins (22,23), and has been implicated in many physiological and pathological processes (24 -27). DM induces an increase in the amount of Hsp90␣ at the luminal surface of the aorta, and this event could be mimicked by treating cultured vascular endothelial cells with high glucose ...

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“…reported to cleave and activate PKA (48). The mechanism by which HG activates PKA and potential involvement of calpain are exciting areas of future investigation.…”

Section: Discussionmentioning

confidence: 99%

Protein Kinase A-dependent Translocation of Hsp90α Impairs Endothelial Nitric-oxide Synthase Activity in High Glucose and Diabetes

Lei

Venkatakrishnan

et al. 2007

Journal of Biological Chemistry

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“…Therefore, they are considered to participate in Ca 2ϩ -associated signal transduction pathways. Calpain activity is associated with the propagation of Ca 2ϩ signaling (21), in some instances converting transient signals to more durable and amplified signals (92). It has been known for some time that HCMV infection induces a substantial increase in cytosolic Ca 2ϩ activity (58).…”

Section: Analysis Of Pest Sequences In P21 Cip1mentioning

confidence: 99%

Degradation of p21 ^cip1 in Cells Productively Infected with Human Cytomegalovirus

Chen

Knutson

Kurosky

et al. 2001

J Virol

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Human cytomegalovirus (HCMV) stimulates arrested cells to enter the cell cycle by activating cyclindependent kinases (Cdks), notably Cdk2. Several mechanisms are involved in the activation of Cdk2. HCMV causes a substantial increase in the abundance of cyclin E and stimulates translocation of Cdk2 from the cytoplasm to the nucleus. Further, the abundance of the Cdk inhibitors (CKIs) p21 cip1/waf1 (p21 cip1 ) and p27 kip1 is substantially reduced. The activity of cyclin E/Cdk2 increases as levels of CKIs, particularly p21 cip1 , fall. We have previously shown that these phenomena contribute to priming the cell for efficient replication of HCMV. In this study, the mechanisms responsible for the decrease in p21 cip1 levels after HCMV infection were investigated by measuring p21 cip1 RNA and protein levels in permissive human lung (LU) fibroblasts after HCMV infection. Northern blot analysis revealed that p21 cip1 RNA levels increased briefly at 3 h after HCMV infection and then decreased to their nadir at 24 h; thereafter, RNA levels increased to about 60% of the preinfection level. Western blot analysis demonstrated that the relative abundance of p21 cip1 protein roughly paralleled the observed changes in initial RNA levels; however, the final levels of protein were much lower than preinfection levels. After a transient increase at 3 h postinfection, p21 cip1 abundance declined sharply over the next 24 h and remained at a very low level through 96 h postinfection. The disparity between p21 cip1 RNA and protein levels suggested that the degradation of p21 cip1 might be affected in HCMV-infected cells. Treatment of HCMV-infected cells with MG132, an inhibitor of proteasome-mediated proteolysis, provided substantial protection of p21 cip1 in mock-infected cells, but MG132 was much less effective in protecting p21 cip1 in HCMV-infected cells. The addition of E64d or Z-Leu-Leu-H, each an inhibitor of calpain activity, to HCMVinfected cells substantially increased the abundance of p21 cip1 in a concentration-dependent manner. To verify that p21 cip1 was a substrate for calpain, purified recombinant p21 cip1 was incubated with either m-calpain or -calpain, which resulted in rapid proteolysis of p21 cip1 . E64d inhibited the proteolysis of p21 cip1 catalyzed by either m-calpain or -calpain. Direct measurement of calpain activity in HCMV-infected LU cells indicated that HCMV infection induced a substantial and sustained increase in calpain activity, although there was no change in the abundance of either m-or -calpain or the endogenous calpain inhibitor calpastatin. The observed increase of calpain activity was consistent with the increases in intracellular free Ca 2؉ and phospholipid degradation in HCMV-infected LU cells reported previously from our laboratory. Considered together, these results suggest that the increase in calpain activity observed following HCMV infection contributes significantly to the reduction of p21 cip1 levels and the resultant cell cycle progression.Human cytomegalovirus (HCMV) infection is wides...

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“…1). Proteolytic regulation of R subunits by cleavage has been reported in rat alveolary type II cells where it is caused by calpain [23]. We propose that cleavage of RI is one of the mechanisms to produce persistent kinase activity of PKA in neuron.…”

Section: Discussionmentioning

confidence: 97%

Serotonin induces selective cleavage of the PKA RI subunit but not RII subunit in Aplysia neurons

Kurosu

Hernández

Schwartz

2007

Biochemical and Biophysical Research Communications

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PKA type I and type II are activated in Aplysia neurons by stimulation with serotonin (5-HT), which causes long-term facilitation (LTF). The proteolysis of the regulatory subunit (R) is thought important for the persistent activation of PKA, which is necessary to produce LTF. In this study, we report that the type I regulatory subunit (RI) and type II regulatory subunit (RII) are differentially regulated by proteolytic cleavage. RI, but not RII, was selectively cleaved after 5-HT treatment for 2 h in Aplysia neurons. Interestingly, the proteasome inhibitor MG132 inhibited the cleavage of RI caused by 5-HT treatment in Aplysia neuron. Besides extracts from Aplysia ganglia treated with 5-HT cleaved 35 S-labeled RI synthesized in vitro, but not 35 S-labeled RII. This suggests that 5-HT induces the activation state of RI-specific proteolytic cleavage.

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Secretagogue-induced proteolysis of cAMP-dependent protein kinase in intact rat alveolar epithelial type II cells

Cited by 17 publications

References 23 publications

Protein Kinase A-dependent Translocation of Hsp90α Impairs Endothelial Nitric-oxide Synthase Activity in High Glucose and Diabetes

Protein Kinase A-dependent Translocation of Hsp90α Impairs Endothelial Nitric-oxide Synthase Activity in High Glucose and Diabetes

Degradation of p21 ^cip1 in Cells Productively Infected with Human Cytomegalovirus

Serotonin induces selective cleavage of the PKA RI subunit but not RII subunit in Aplysia neurons

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Secretagogue-induced proteolysis of cAMP-dependent protein kinase in intact rat alveolar epithelial type II cells

Cited by 17 publications

References 23 publications

Protein Kinase A-dependent Translocation of Hsp90α Impairs Endothelial Nitric-oxide Synthase Activity in High Glucose and Diabetes

Protein Kinase A-dependent Translocation of Hsp90α Impairs Endothelial Nitric-oxide Synthase Activity in High Glucose and Diabetes

Degradation of p21 cip1 in Cells Productively Infected with Human Cytomegalovirus

Serotonin induces selective cleavage of the PKA RI subunit but not RII subunit in Aplysia neurons

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Degradation of p21 ^cip1 in Cells Productively Infected with Human Cytomegalovirus