Agonist-induced Ca2+ entry determined by inositol 1,4,5-trisphosphate recognition.
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 Ca2+ entry in response to receptor activation is attributed to the absence of Ca2+ release. We reveal in this article that IP3R recognition of IP3 determines agonist-induced Ca2+ entry (ACE), independent of its Ca2+ release activity. In DT40 IP3R(-/-) cells, endogenous ACE can be rescued with type 1 IP3R mutants (both a DeltaC-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 IP3 binding (both the Delta90-110 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.
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Damian B
DB
van Rossum
Randen L
RL
Patterson
Kirill
K
Kiselyov
Darren
D
Boehning
Roxanne K
RK
Barrow
Donald L
DL
Gill
Solomon H
SH
Snyder
D019943:Amino Acid Substitution; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D016716:PC12 Cells; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium