Investigation of mechanism underlying the nuclear export of poly C binding protein 1 in neuronal cells

Recently, poly C binding protein 1 (PCBP) has been shown to regulate the gene expression of mu‐opioid receptor (MOR), which is mainly located in the central nervous system. We therefore examined the subcellular distribution of PCBP in neuronal cells. A mammalian expression vector containing the EGFP‐PCBP fusion protein was generated and transfected into neuronal cells. The expression pattern of PCBP in neuronal cells was imaged using the laser scanning confocal microscope. Results demonstrated that PCBP was present throughout the nucleus and cytoplasm, with a punctated nuclear staining pattern. However, its nuclear distribution was stronger than its cytoplasmic distribution. The mechanism of nuclear trafficking of PCBP in neuronal cells was then investigated, particularly focused on the nuclear export. CRM1 (exportin 1) is known to play an important role in exporting certain proteins from nucleus into the cytoplasm. This export function can be blocked by leptomycin B (LMB) treatment. To determine if CRM1 mediates the nuclear export of PCBP, we treated EGFP‐PCBP transfected cells with or without LMB. Our preliminary results demonstrated that the nuclear distribution of PCBP was enhanced by LMB treatment as compared to that of the non‐treated cells. Although an additional route of exporting PCBP might exist since LMB treatment did not completely block the nuclear export of PCBP in neuronal cells. This data suggested that CRM1 mediated, at least partially, the nuclear export of PCBP in neuronal cells. This research was supported by NIH research grant DA‐016673.