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α‐Synuclein exhibits competitive interaction between calmodulin and synthetic membranes
Author(s) -
Lee Daekyun,
Lee SunYoung,
Lee EuiNam,
Chang ChungSoon,
Paik Seung R.
Publication year - 2002
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2002.01024.x
Subject(s) - calmodulin , chemistry , biophysics , calcium , biochemistry , biology , enzyme , organic chemistry
α‐Synuclein, a pathological component of Parkinson's disease by constituting the Lewy bodies, has been suggested to be involved in membrane biogenesis via induction of amphipathic α‐helices. Since the amphipathic α‐helix is also known as a recognition signal of calmodulin for its target proteins, molecular interaction between α‐synuclein and calmodulin has been investigated. By employing a chemical coupling reagent of N ‐(ethoxycarbonyl)‐2‐ethoxy‐1,2‐dihydroquinoline, α‐synuclein has been shown to yield a heterodimeric 1 : 1 complex with calmodulin on sodium dodecyl sulfate–polyacrylamide gel electrophoresis in the presence and even absence of calcium, whereas β‐synuclein was more dependent upon calcium for its calmodulin interaction. The selective calmodulin interaction of α‐synuclein in the absence of calcium was also demonstrated with the aggregation kinetics of the synucleins in which only the α‐synuclein aggregation was affected by calmodulin. A reversible binding assay confirmed that α‐synuclein interacted with the Ca 2+ ‐free as well as the Ca 2+ ‐bound calmodulins with almost identical K d s of 0.35 µ m and 0.31 µ m , respectively, while β‐synuclein preferentially recognized the Ca 2+ ‐bound form with a K d of 0.68 µ m . By using a C‐terminally truncated α‐synuclein of α‐syn97, the calmodulin binding site(s) on α‐synuclein was(were) shown to be located on the N‐terminal region where the amphipathic α‐helices have been suggested to be induced upon membrane interaction. By employing liposome and calmodulin in a state of being either soluble or immobilized on agarose, actual competition of α‐synuclein between membranes and calmodulin was demonstrated with the observation that α‐synuclein previously bound to the liposome was released upon specific interaction with the calmodulins. Taken together, these data may suggest that α‐synuclein could act not only as a negative regulator for calmodulin in the presence and even absence of calcium, but it could also exert its activity at the interface between calmodulin and membranes.