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Identification of a peptide sequence in albumin that potentiates superoxide production by microglia
1Department of Physiology, Ehime University School of Medicine, Ehime, Japan. yoichi@dbs.p.kanazawa-u.ac.jp
Abstract:
Microglial activation has recently been recognized as a cause of damage in various neurodegenerative diseases. A possible mechanism underlying this damage is the activation of microglia by serum factors leaked through a disruption of the blood-brain barrier, which in turn trigger microglial cell proliferation and the release of various substances toxic to neurons, such as superoxide (O(2)(-)). We recently reported that serum albumin enhanced O(2)(-) production in cultured rat microglia stimulated by phorbol ester. In the present report, we identify the active site of this enhancement within the albumin molecule. We purified an active subfragment from trypsin-treated bovine serum albumin that was composed of 12-mer and 33-mer peptides connected by a disulfide bond. The chemically synthesized 12-mer peptide showed activity within a concentration range ( approximately 10(-7) M:) equivalent to that of albumin. The activities of a series of synthesized peptides conclusively indicated that the minimum active sequence was Leu-His-Thr-Leu. The present study may shed light on the mechanism of neuronal cell damage in various neurodegenerative diseases.
Insights
Serum albumin contributes to neurodegeneration by activating microglia, releasing toxic superoxide. Researchers identified a specific peptide sequence (Leu-His-Thr-Leu) in albumin responsible for this harmful microglial activation.
Area of Science:
- Neuroscience
- Immunology
Background:
- Microglial activation is implicated in neurodegenerative disease pathology.
- Blood-brain barrier disruption allows serum factors to activate microglia, leading to neuronal damage via substances like superoxide (O(2)(-)).
Purpose of the Study:
- To identify the specific site within serum albumin responsible for enhancing microglial superoxide production.
- To elucidate the molecular mechanism of albumin-induced microglial activation.
Main Methods:
- Purification of an active subfragment from trypsin-treated bovine serum albumin.
- Chemical synthesis of peptides, including a 12-mer peptide and a minimal active sequence.
- Assay of superoxide production in cultured rat microglia stimulated with phorbol ester and varying peptide concentrations.
Main Results:
- An active subfragment, a disulfide-linked 12-mer and 33-mer peptide, was purified from bovine serum albumin.
- The chemically synthesized 12-mer peptide demonstrated significant activity at nanomolar concentrations.
- The minimal active sequence responsible for enhancing superoxide production was identified as Leu-His-Thr-Leu.
Conclusions:
- A specific peptide sequence in serum albumin directly enhances microglial superoxide production.
- This finding provides a molecular basis for how serum factors contribute to neuronal damage in neurodegenerative conditions.
- Targeting this albumin-derived peptide may offer a novel therapeutic strategy for neurodegenerative diseases.