Myristoylation alone is sufficient for PKA catalytic subunits to fractionally associate with the plasma membrane to regulate neuronal functions

Abstract

Myristoylation is a post-translational modification that plays diverse functional roles in many protein species. The myristate moiety is considered insufficient for protein-membrane associations unless additional membrane-affinity motifs, such as a stretch of positively charged residues, are present. Here, we report that the electrically neutral N-terminal fragment of the protein kinase A catalytic subunit (PKA-C), in which myristoylation is the only functional motif, is sufficient for membrane association. This myristoylation can associate a fraction of PKA-C molecules or fluorescent proteins (FPs) to the plasma membrane in neuronal dendrites. The net neutral charge of PKA-C is evolutionally conserved, even though its membrane affinity can be readily tuned by changing charges near the myristoylation site. The observed membrane association, while moderate, is sufficient to concentrate PKA activity at the membrane by nearly 20-fold, and is required for PKA regulation of AMPA receptors at neuronal synapses. Our results indicate that myristoylation alone may be sufficient to drive functionally significant membrane association in the absence of assisting motifs. This provides a revised foundation for the understanding of how myristoylation regulates protein functions.