Intracellular membrane association of Aplysia cAMP phosphodiesterase long- and short-form via different targeting mechanisms [Cell Biology]

July 30th, 2014 by Kim, K.-H., Jun, Y.-W., Park, Y., Lee, J.-A., Suh, B.-C., Lim, C.-S., Lee, Y.-S., Kaang, B.-K., Jang, D.-J.

Phosphodiesterases (PDEs) play key roles in cAMP compartmentalization, which is required for intracellular signaling processes, through specific subcellular targeting. Previously, we showed that long- and short-form of Aplysia PDE4 (ApPDE4), which are localized to the membranes of distinct subcellular organelles, play key roles in 5-HT-induced synaptic facilitation in Aplysia sensory to motor synapses. However, the molecular mechanism of the isoform-specific distinct membrane targeting was not clear. In this study, we further investigated the molecular mechanism of the membrane targeting of ApPDE4 long- and short-form. We found that the membrane targeting of the long-form was mediated by hydrophobic interactions mainly via 16 amino acids at the N-terminal region, whereas the short-form was targeted solely to the plasma membrane mainly by nonspecific electrostatic interactions between their N-terminus and the negatively charged lipids such as the phosphatidylinositol (PI) polyphosphates PI4P and PI(4,5)P2, which are embedded in the inner leaflet of the plasma membrane. Moreover, oligomerization of the long- or the short-form by interaction of their respective upstream conserved region (UCR) domains, UCR1 and UCR2, enhanced their plasma membrane targeting. These results suggest that the long- and the short-form of ApPDE4 are distinctly targeted to intracellular membranes through their direct association with the membranes via hydrophobic and electrostatic interactions, respectively.