alpha-2,8-Polysialic acid is the neuronal surface receptor of antennapedia homeobox peptide.

A synthetic peptide that is 60 amino acids in length and corresponds to the homeobox sequence of antennapedia protein (pAntp) is specifically and efficiently captured by neurons in culture and conveyed to their nuclei. The internalization process is followed by a strong induction of neuronal morphological differentiation. In the study described here, all treatments masking or removing the alpha-2,8-polysialic acid (PSA) chains specific to the neuronal cell adhesion molecule (NCAM) were found to block the penetration of pAntp and abolish its morphogenetic effects. Structural comparison between PSA and double-stranded DNA suggests that a sequence of eight sialic acid residues can mimic one large groove of the DNA. We propose that this structural similarity is the basis for the property of NCAM polysialic acid to participate in the internalization of the homebox polypeptide.