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Human keratinocytes release ATP and utilize three mechanisms for nucleotide interconversion at the cell surface
Helen E Burrell1, Brenda Wlodarski, Brian J Foster
1Department of Human Anatomy & Cell Biology, School of Biomedical Sciences, University of Liverpool, The Sherrington Buildings, UK. H.E.Burrell@liv.ac.uk
The Journal of Biological Chemistry
|June 17, 2005
Summary
Skin cells, keratinocytes, generate extracellular ATP through multiple pathways, including cell surface enzymes. This finding clarifies how nucleotides regulate skin cell functions and healing.
Area of Science:
- Biochemistry
- Dermatology
- Cell Biology
Background:
- Nucleotides activate P2 receptors, crucial for autocrine/paracrine signaling in tissues.
- In the epidermis, nucleotides influence keratinocyte proliferation, differentiation, and apoptosis.
Purpose of the Study:
- To investigate extracellular ATP generation mechanisms in HaCaT keratinocytes.
- To identify enzymes involved in nucleotide interconversion and ATP synthesis at the cell surface.
- To understand the role of extracellular nucleotides in epidermal homeostasis and wound healing.
Main Methods:
- Luciferin-luciferase luminometry to measure ATP concentration.
- Pharmacological inhibitors to identify enzyme involvement.
- Confocal microscopy and immunohistochemistry for protein localization.
Main Results:
- HaCaT keratinocytes release ATP into the culture medium.
- Cell surface enzymes like adenylate kinase, F(1)F(0) ATP synthase, and nucleoside diphosphokinase (NDPK) contribute to ATP generation.
- GTP acts as a phosphate donor for ATP synthesis.
- The reverse reaction of adenylate kinase utilizing AMP is proposed to account for remaining ATP levels.
- Enzymes showed differential localization in normal human skin, with cell surface expression in differentiated layers.
Conclusions:
- Multiple enzymatic pathways contribute to extracellular ATP production in keratinocytes.
- Understanding these mechanisms enhances knowledge of nucleotide signaling in skin homeostasis and wound repair.
- Identified potential sources of extracellular ATP for P2 receptor activation in the epidermis.