Development of a novel alpha7-nicotinic acetylcholine receptor-selective cell-penetrating peptide for intracellular cargo transport.

Cell membranes present barriers to the intracellular delivery of therapeutic agents. This impediment is frequently exacerbated by the hydrophobic characteristics of many such molecules, ultimately reducing the efficiency of their cellular uptake and therapeutic effectiveness. Therapeutics are being created that exploit natural bypass mechanisms by forming complexes with cell-penetrating peptides (CPPs) derived from viruses. However, current CPPs lack the ability to selectively target precise cellular macromolecules. As a result, they are distributed broadly and cause off-target side effects. Neurotropic CPPs derived from the rabies virus glycoprotein (RVG) can access the brain by binding to plasma membrane targets, including, but not exclusively, nicotinic acetylcholine receptors (nAChRs). To overcome this barrier of minimal target selectivity, we designed several chimeric peptides composed of regions from the RVG and α-bungarotoxin, an α7 subtype-selective protein. Using human nAChRs expressed in Xenopus laevis oocytes, we screened the selectivity of our peptides using two-electrode voltage clamp electrophysiology. We identified a peptide with improved α7 nAChR subtype selectivity and apparent potency compared to the control RVG peptide. Using mammalian Neuro-2a cells, we demonstrated that our peptide depends on α7 nAChR plasma membrane expression to internalize and carry small-molecule payloads into neuronal-like cells without significant cytotoxic effects. Our novel α7 nAChR subtype-selective CPP may be useful in research applications requiring cargo delivery. Translationally, our α7 nAChR-selective CPP holds potential to be a dual drug delivery system to transport cargo into the brain for the treatment of neurological diseases.