NH2-Terminal targeting motifs direct dual specificity A-kinase-anchoring protein 1 (D-AKAP1) to either mitochondria or endoplasmic reticulum

J Cell Biol. 1999 May 31;145(5):951-9. doi: 10.1083/jcb.145.5.951.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • A Kinase Anchor Proteins
  • Adaptor Proteins, Signal Transducing*
  • Amino Acid Sequence
  • Animals
  • Biological Transport
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Line
  • Cell-Free System
  • Endoplasmic Reticulum / metabolism*
  • Fibroblasts / metabolism*
  • Fibroblasts / ultrastructure*
  • Mice
  • Mitochondria / metabolism*
  • Molecular Sequence Data
  • RNA Splicing
  • Structure-Activity Relationship

Substances

  • A Kinase Anchor Proteins
  • Adaptor Proteins, Signal Transducing
  • Akap1 protein, mouse
  • Carrier Proteins