TY - JOUR
T1 - Phosphatidylinositol phosphates as co-activators of Ca2+ binding to C2 domains of synaptotagmin 1
AU - Li, LiYi
AU - Shin, Ok Ho
AU - Rhee, Jeong Seop
AU - Araç, Demet
AU - Rah, Jong Cheol
AU - Rizo-Rey, Jose
AU - Südhof, Thomas
AU - Rosenmund, Christian
PY - 2006/6/9
Y1 - 2006/6/9
N2 - Ca2+-dependent phospholipid binding to the C2A and C2B domains of synaptotagmin 1 is thought to trigger fast neurotransmitter release, but only Ca2+ binding to the C2B domain is essential for release. To investigate the underlying mechanism, we have compared the role of basic residues in Ca2+/phospholipid binding and in release. Mutations in a polybasic sequenceonthe side of the C 2B domain β-sandwich or in a basic residue in a top Ca 2+-binding loop of the C2A domain (R233) cause comparable decreases in the apparent Ca2+ affinity of synaptotagmin 1 and the Ca2+ sensitivity of release, whereas mutation of the residue homologous to Arg233 in the C2B domain (Lys366) has no effect. Phosphatidylinositol polyphosphates co-activate Ca 2+-dependent and -independent phospholipid binding to synaptotagmin 1, but the effects of these mutations on release only correlate with their effects on the Ca2+-dependent component. These results reveal clear distinctions in the Ca2+-dependent phospholipid binding modes of the synaptotagmin 1 C2 domains that may underlie their functional asymmetry and suggest that phosphatidylinositol polyphosphates may serve as physiological modulators of Ca2+ affinity of synaptotagmin 1 in vivo.
AB - Ca2+-dependent phospholipid binding to the C2A and C2B domains of synaptotagmin 1 is thought to trigger fast neurotransmitter release, but only Ca2+ binding to the C2B domain is essential for release. To investigate the underlying mechanism, we have compared the role of basic residues in Ca2+/phospholipid binding and in release. Mutations in a polybasic sequenceonthe side of the C 2B domain β-sandwich or in a basic residue in a top Ca 2+-binding loop of the C2A domain (R233) cause comparable decreases in the apparent Ca2+ affinity of synaptotagmin 1 and the Ca2+ sensitivity of release, whereas mutation of the residue homologous to Arg233 in the C2B domain (Lys366) has no effect. Phosphatidylinositol polyphosphates co-activate Ca 2+-dependent and -independent phospholipid binding to synaptotagmin 1, but the effects of these mutations on release only correlate with their effects on the Ca2+-dependent component. These results reveal clear distinctions in the Ca2+-dependent phospholipid binding modes of the synaptotagmin 1 C2 domains that may underlie their functional asymmetry and suggest that phosphatidylinositol polyphosphates may serve as physiological modulators of Ca2+ affinity of synaptotagmin 1 in vivo.
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U2 - 10.1074/jbc.M600888200
DO - 10.1074/jbc.M600888200
M3 - Article
C2 - 16595652
AN - SCOPUS:33744921671
SN - 0021-9258
VL - 281
SP - 15845
EP - 15852
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 23
ER -