The Study Of A Novel Cell-penetrating Peptide From Porcine Circovirus

Porcine circovirus type 2 (PCV2) is one of the smallest and non-enveloped DNA viruses. It belongs to the genus Circovirus of the family Circoviridae, which is associated with a number of diseases, collectively named as the porcine circovirus diseases (PCVDs). PCV2 is nowadays regarded as one of the most important pathogens and causing significant economic losses in the swine industry worldwide. The capsid protein (Cap) of PCV2 is the sole viral structure protein and the main antigenic determinant of this virus. Amino acid (aa) sequence analysis indicated that the NH2-terminus (NT) of the PCV2 Cap contains a nuclear localization signal (NLS) domain and enriches with positively charged aa residues.In this study, we investigated the functions of the NLS domain of the PCV2 Cap as a cell penetrating peptide (CPP) and we tried to identify the NLS associated pathogenicity. The synthesized peptide (NLS-A) containing the first 20 aa residues of the NLS domain, can penetrate cell membranes efficiently via an actin-dependent pathway. Therefore it might be recognized as a cell-penetrating peptide (CPP), which is similar to the TAT peptide. The NLS also carry the macromolecules into the cells if fused with enhanced green fluorescence protein (eGFP). The internalization mechanism of the NLS-A has also been investigated in the study. When the concentration of the NLS-A peptide is lower than 10 ?M in culture, the peptide had a punctate distribution pattern in cytoplasm, indicating that it might enter the cells via an endocytic pathway, however an even distribution pattern of the NLS-A in cells was observed when the concentration of the peptide is over 10 ?M. Our results also suggest that the NLS-A has a higher cell-penetrating capacity than the TAT peptide. So the NLS-A might be developed as an efficient drug carrier and can deliver the medicines into the targeted cells for the clinic therapy in future.