It has been considered that Ca2+ release is the causal trigger for Ca2+ entry after receptor activation. In DT40 B cells devoid of inositol 1,4,5-trisphosphate receptors (IP3R), the lack of Ca 2+ entry in response to receptor activation is attributed to the absence of Ca2+ release. We reveal in this article that IP 3R recognition of IP3 determines agonist-induced Ca 2+ entry (ACE), independent of its Ca2+ release activity. In DT40 IP3R-/- cells, endogenous ACE can be rescued with type 1 IP3R mutants (both a ΔC-terminal truncation mutant and a D2550A pore mutant), which are defective in Ca2+ release channel activity. Thus, in response to B cell receptor activation, ACE is restored in an IP3R-dependent manner without Ca2+ store release. Conversely, ACE cannot be rescued with mutant IP3Rs lacking IP 3 binding (both the Δ90-110 and R265Q IP3-binding site mutants). We conclude that an IP3-dependent conformational change in the IP3R, not endoplasmic reticulum Ca2+ pool release, triggers ACE.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Feb 22 2004|
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