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Picomolar concentrations of lead stimulate brain protein kinase C
1Department of Pediatrics, University of Michigan Medical School, Ann Arbor 48109-0570.
Abstract:
Recent growth studies in children suggest that there is no threshold for adverse effects from the universal exposure to inorganic lead. The biochemical mechanisms mediating low-level toxicity are unclear, but in several biological systems, lead alters calcium-mediated cellular processes and may mimic calcium in binding to regulatory proteins. Here we present evidence that lead stimulates diacylglycerol-activated calcium and phospholipid-dependent protein kinase, protein kinase C, partially purified from rat brain. Picomolar concentrations of lead are equivalent to micromolar calcium in kinase activation, so this regulatory enzyme is sensitive to the lead levels expected from current environmental exposure.
Insights
This study shows that even low environmental lead exposure can activate protein kinase C, a key enzyme in cells. This suggests lead disrupts normal cell signaling at very low levels, impacting children's health.
Area of Science:
- Biochemistry
- Toxicology
- Neuroscience
Background:
- Universal exposure to inorganic lead poses risks, with no identified safe threshold for adverse effects in children.
- The biochemical pathways of low-level lead toxicity remain largely unknown.
- Lead is known to interfere with calcium-mediated cellular functions and can mimic calcium's role in protein interactions.
Purpose of the Study:
- To investigate the biochemical mechanisms by which low-level lead exposure exerts toxicity.
- To determine if lead can directly affect critical cellular signaling enzymes.
- To assess the sensitivity of cellular processes to environmentally relevant lead concentrations.
Main Methods:
- Partial purification of protein kinase C from rat brain tissue.
- Assaying protein kinase C activity in the presence of varying lead and calcium concentrations.
- Comparing the potency of lead and calcium in activating the enzyme.
Main Results:
- Lead was found to stimulate diacylglycerol-activated, calcium and phospholipid-dependent protein kinase (protein kinase C).
- Picomolar concentrations of lead demonstrated kinase activation potency comparable to micromolar concentrations of calcium.
- This indicates protein kinase C is highly sensitive to lead levels found in current environmental exposures.
Conclusions:
- The enzyme protein kinase C is a potential target for low-level lead toxicity.
- Lead's ability to activate protein kinase C at picomolar levels provides a biochemical mechanism for its adverse effects.
- Findings highlight the sensitivity of cellular regulatory enzymes to environmental lead, underscoring public health concerns.