TY - JOUR
T1 - Small GTPase Rab11b regulates degradation of surface membrane L-type Cav1.2 channels
AU - Best, Jabe M.
AU - Foell, Jason D.
AU - Buss, Courtney R.
AU - Delisle, Brian P.
AU - Balijepalli, Ravi C.
AU - January, Craig T.
AU - Kamp, Timothy J.
PY - 2011/5
Y1 - 2011/5
N2 - L-type Ca2+ channels (LTCCs) play a critical role in Ca2+-dependent signaling processes in a variety of cell types. The number of functional LTCCs at the plasma membrane strongly influences the strength and duration of Ca2+ signals. Recent studies demonstrated that endosomal trafficking provides a mechanism for dynamic changes in LTCC surface membrane density. The purpose of the current study was to determine whether the small GTPase Rab11b, a known regulator of endosomal recycling, impacts plasmalemmal expression of Cav1.2 LTCCs. Disruption of endogenous Rab11b function with a dominant negative Rab11b S25N mutant led to a significant 64% increase in peak L-type Ba2+ current (IBa,L) in human embryonic kidney (HEK)293 cells. Short-hairpin RNA (shRNA)-mediated knockdown of Rab11b also significantly increased peak IBa,L by 66% compared when with cells transfected with control shRNA, whereas knockdown of Rab11a did not impact IBa,L. Rab11b S25N led to a 1.7-fold increase in plasma membrane density of hemagglutinin epitope-tagged Cav1.2 expressed in HEK293 cells. Cell surface biotinylation experiments demonstrated that Rab11b S25N does not significantly impact anterograde trafficking of LTCCs to the surface membrane but rather slows degradation of plasmalemmal Cav1.2 channels. We further demonstrated Rab11b expression in ventricular myocardium and showed that Rab11b S25N significantly increases peak IBa,L by 98% in neonatal mouse cardiac myocytes. These findings reveal a novel role for Rab11b in limiting, rather than promoting, the plasma membrane expression of Cav1.2 LTCCs in contrast to its effects on other ion channels including human ethera- go-go-related gene (hERG) K+ channels and cystic fibrosis transmembrane conductance regulator. This suggests Rab11b differentially regulates the trafficking of distinct cargo and extends our understanding of how endosomal transport impacts the functional expression of LTCCs.
AB - L-type Ca2+ channels (LTCCs) play a critical role in Ca2+-dependent signaling processes in a variety of cell types. The number of functional LTCCs at the plasma membrane strongly influences the strength and duration of Ca2+ signals. Recent studies demonstrated that endosomal trafficking provides a mechanism for dynamic changes in LTCC surface membrane density. The purpose of the current study was to determine whether the small GTPase Rab11b, a known regulator of endosomal recycling, impacts plasmalemmal expression of Cav1.2 LTCCs. Disruption of endogenous Rab11b function with a dominant negative Rab11b S25N mutant led to a significant 64% increase in peak L-type Ba2+ current (IBa,L) in human embryonic kidney (HEK)293 cells. Short-hairpin RNA (shRNA)-mediated knockdown of Rab11b also significantly increased peak IBa,L by 66% compared when with cells transfected with control shRNA, whereas knockdown of Rab11a did not impact IBa,L. Rab11b S25N led to a 1.7-fold increase in plasma membrane density of hemagglutinin epitope-tagged Cav1.2 expressed in HEK293 cells. Cell surface biotinylation experiments demonstrated that Rab11b S25N does not significantly impact anterograde trafficking of LTCCs to the surface membrane but rather slows degradation of plasmalemmal Cav1.2 channels. We further demonstrated Rab11b expression in ventricular myocardium and showed that Rab11b S25N significantly increases peak IBa,L by 98% in neonatal mouse cardiac myocytes. These findings reveal a novel role for Rab11b in limiting, rather than promoting, the plasma membrane expression of Cav1.2 LTCCs in contrast to its effects on other ion channels including human ethera- go-go-related gene (hERG) K+ channels and cystic fibrosis transmembrane conductance regulator. This suggests Rab11b differentially regulates the trafficking of distinct cargo and extends our understanding of how endosomal transport impacts the functional expression of LTCCs.
KW - Electrophysiology
KW - Endosomal trafficking
KW - Heart
KW - Ion channels
UR - http://www.scopus.com/inward/record.url?scp=79955552940&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79955552940&partnerID=8YFLogxK
U2 - 10.1152/ajpcell.00288.2010
DO - 10.1152/ajpcell.00288.2010
M3 - Article
C2 - 21248079
AN - SCOPUS:79955552940
SN - 0363-6143
VL - 300
SP - C1023-C1033
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
IS - 5
ER -