NH2-Terminal targeting motifs direct dual specificity A-kinase-anchoring protein 1 (D-AKAP1) to either mitochondria or endoplasmic reticulum.
Subcellular localization directed by specific targeting motifs is an emerging theme for regulating signal transduction pathways. For cAMP-dependent protein kinase (PKA), this is achieved primarily by its association with A-kinase-anchoring proteins (AKAPs). Dual specificity AKAP1, (D-AKAP1) binds to both type I and type II regulatory subunits and has two NH2-terminal (N0 and N1) and two COOH-terminal (C1 and C2) splice variants (. J. Biol. Chem. 272:8057). Here we report that the splice variants of D-AKAP1 are expressed in a tissue-specific manner with the NH2-terminal motifs serving as switches to localize D-AKAP1 at different sites. Northern blots showed that the N1 splice is expressed primarily in liver, while the C1 splice is predominant in testis. The C2 splice shows a general expression pattern. Microinjecting expression constructs of D-AKAP1(N0) epitope-tagged at either the NH2 or the COOH terminus showed their localization to the mitochondria based on immunocytochemistry. Deletion of N0(1-30) abolished mitochondrial targeting while N0(1-30)-GFP localized to mitochondria. Residues 1-30 of N0 are therefore necessary and sufficient for mitochondria targeting. Addition of the 33 residues of N1 targets D-AKAP1 to the ER and residues 1-63 fused to GFP are necessary and sufficient for ER targeting. Residues 14-33 of N1 are especially important for targeting to ER; however, residues 1-33 alone fused to GFP gave a diffuse distribution. N1(14-33) thus serves two functions: (a) it suppresses the mitochondrial-targeting motif located within residues 1-30 of N0 and (b) it exposes an ER-targeting motif that is at least partially contained within the N0(1-30) motif. This represents the first example of a differentially targeted AKAP and adds an additional level of complexity to the PKA signaling network.
Huang
L J
LJ
Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0654, USA.
Wang
L
L
Ma
Y
Y
Durick
K
K
Perkins
G
G
Deerinck
T J
TJ
Ellisman
M H
MH
Taylor
S S
SS
D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002474:Cell-Free System; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism* / Q000648:ultrastructure*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D012326:RNA Splicing; D013329:Structure-Activity Relationship
D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; C486333:Akap1 protein, mouse; D002352:Carrier Proteins