The inositol 1,4,5-trisphosphate receptor regulates autophagy through its interaction with Beclin 1.
The inositol 1,4,5-trisphosphate receptor (IP(3)R) is a major regulator of apoptotic signaling. Through interactions with members of the Bcl-2 family of proteins, it drives calcium (Ca(2+)) transients from the endoplasmic reticulum (ER) to mitochondria, thereby establishing a functional and physical link between these organelles. Importantly, the IP(3)R also regulates autophagy, and in particular, its inhibition/depletion strongly induces macroautophagy. Here, we show that the IP(3)R antagonist xestospongin B induces autophagy by disrupting a molecular complex formed by the IP(3)R and Beclin 1, an interaction that is increased or inhibited by overexpression or knockdown of Bcl-2, respectively. An effect of Beclin 1 on Ca(2+) homeostasis was discarded as siRNA-mediated knockdown of Beclin 1 did not affect cytosolic or luminal ER Ca(2+) levels. Xestospongin B- or starvation-induced autophagy was inhibited by overexpression of the IP(3)R ligand-binding domain, which coimmunoprecipitated with Beclin 1. These results identify IP(3)R as a new regulator of the Beclin 1 complex that may bridge signals converging on the ER and initial phagophore formation.
Vicencio
J M
JM
INSERM, U848, F-94805 Villejuif, France.
Ortiz
C
C
Criollo
A
A
Jones
A W E
AW
Kepp
O
O
Galluzzi
L
L
Joza
N
N
Vitale
I
I
Morselli
E
E
Tailler
M
M
Castedo
M
M
Maiuri
M C
MC
Molgó
J
J
Szabadkai
G
G
Lavandero
S
S
Kroemer
G
G