Protein kinase A site-specific phosphorylation regulates ATP-binding cassette A1 (ABCA1)-mediated phospholipid efflux.
ATP-binding cassette A1 (ABCA1) is a key mediator of cholesterol and phospholipid efflux to apolipoprotein particles. We show that ABCA1 is a constitutively phosphorylated protein in both RAW macrophages and in a human embryonic kidney cell line expressing ABCA1. Furthermore, we demonstrate that phosphorylation of ABCA1 is mediated by protein kinase A (PKA) or a PKA-like kinase in vivo. Through site-directed mutagenesis studies of consensus PKA phosphorylation sites and in vitro PKA kinase assays, we show that Ser-1042 and Ser-2054, located in the nucleotide binding domains of ABCA1, are major phosphorylation sites for PKA. ApoA-I-dependent phospholipid efflux was decreased significantly by mutation of Ser-2054 alone and Ser-1042/Ser-2054 but was not significantly impaired with Ser-1042 alone. The mechanism by which ABCA1 phosphorylation affected ApoA-I-dependent phospholipid efflux did not involve either alterations in ApoA-I binding or changes in ABCA1 protein stability. These studies demonstrate a novel serine (Ser-2054) on the ABCA1 protein crucial for PKA phosphorylation and for regulation of ABCA1 transporter activity.
Center for Molecular Medicine and Therapeutics, Department of Medical Genetics and Children's and Women's Hospital, University of British Columbia, Vancouver, Canada.
Raymond H
RH
See
Rosalinda A
RA
Caday-Malcolm
Roshni R
RR
Singaraja
Steven
S
Zhou
Anthony
A
Silverston
Mary T
MT
Huber
Josh
J
Moran
Erick R
ER
James
Rozmin
R
Janoo
Jane M
JM
Savill
Veronique
V
Rigot
Lin-Hua
LH
Zhang
Minghan
M
Wang
Giovanna
G
Chimini
Cheryl L
CL
Wellington
Sherrie R
SR
Tafuri
Michael R
MR
Hayden
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010743:Phospholipids / Q000378:metabolism*; D010766:Phosphorylation; D012694:Serine; D013329:Structure-Activity Relationship
C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D010743:Phospholipids; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases