Pharmacological AMP kinase activators target the nucleolar organization and control cell proliferation
Mohamed Kodiha1, Ali Salimi1, Yi Meng Wang1
1Department of Physiology, McGill University, Montreal, Quebec, Canada.
Aims:
Phenformin, resveratrol and AICAR stimulate the energy sensor 5'-AMP activated kinase (AMPK) and inhibit the first step of ribosome biogenesis, de novo RNA synthesis in nucleoli. Nucleolar activities are relevant to human health, because ribosome production is crucial to the development of diabetic complications. Although the function of nucleoli relies on their organization, the impact of AMPK activators on nucleolar structures is not known. Here, we addressed this question by examining four nucleolar proteins that are essential for ribosome biogenesis.
Methods:
Kidney cells were selected as model system, because diabetic nephropathy is one of the complications associated with diabetes mellitus. To determine the impact of pharmacological agents on nucleoli, we focused on the subcellular and subnuclear distribution of B23/nucleophosmin, fibrillarin, nucleolin and RPA194. This was achieved by quantitative confocal microscopy at the single-cell level in combination with cell fractionation and quantitative Western blotting.
Results:
AMPK activators induced the re-organization of nucleoli, which was accompanied by changes in cell proliferation. Among the compounds tested, phenformin and resveratrol had the most pronounced impact on nucleolar organization. For B23, fibrillarin, nucleolin and RPA194, both agents (i) altered the nucleocytoplasmic distribution and nucleolar association and (ii) reduced significantly the retention in the nucleus. (iii) Phenformin and resveratrol also increased significantly the total concentration of B23 and nucleolin.
Conclusions:
AMPK activators have unique effects on the subcellular localization, nuclear retention and abundance of nucleolar proteins. We propose that the combination of these events inhibits de novo ribosomal RNA synthesis and modulates cell proliferation. Our studies identified nucleolin as a target that is especially sensitive to pharmacological AMPK activators. Because of its response to pharmacological agents, nucleolin represents a potential biomarker for the development of drugs that diminish diabetic renal hypertrophy.
Insights
AMPK activators like phenformin and resveratrol alter nucleolar protein organization, impacting cell proliferation. Nucleolin is a key target, potentially serving as a biomarker for diabetic kidney disease treatments.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Nucleolar activities, including ribosome biogenesis, are critical for cellular function and implicated in diabetic complications.
- The energy sensor 5'-AMP-activated kinase (AMPK) plays a role in regulating cellular metabolism and ribosome production.
- The impact of AMPK activators on nucleolar structure and organization remains largely unknown.
Purpose of the Study:
- To investigate the effects of AMPK activators on nucleolar structure and the distribution of key nucleolar proteins.
- To determine if AMPK activators influence the organization of nucleoli, which are essential for ribosome biogenesis.
- To identify potential therapeutic targets for diabetic complications by examining nucleolar protein responses.
Main Methods:
- Utilized kidney cells as a model system due to their relevance in diabetic nephropathy.
- Examined the subcellular and subnuclear distribution of nucleolar proteins (B23/nucleophosmin, fibrillarin, nucleolin, RPA194) using quantitative confocal microscopy.
- Employed cell fractionation and quantitative Western blotting to assess protein levels and localization.
Main Results:
- AMPK activators, particularly phenformin and resveratrol, significantly reorganized nucleoli, affecting cell proliferation.
- These agents altered the nucleocytoplasmic distribution and nucleolar association of B23, fibrillarin, nucleolin, and RPA194.
- Phenformin and resveratrol reduced the nuclear retention of these proteins and increased the total concentration of B23 and nucleolin.
Conclusions:
- AMPK activators induce distinct changes in the subcellular localization, nuclear retention, and abundance of nucleolar proteins.
- These modifications are proposed to inhibit ribosomal RNA synthesis and modulate cell proliferation.
- Nucleolin emerged as a sensitive target for pharmacological AMPK activators, suggesting its potential as a biomarker for drugs treating diabetic renal hypertrophy.
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