Molecular characterization of pannexins in the lens

[摘要] Purpose: Cell communication in the lens is critical for thelife-long homeostasis of this tissue. Abundant gap junctions andcell-cell fusions are reported to be indispensable to the metabolicrequirements and optical properties of the highly interconnectedsyncytial lens tissue. The expression of the recently characterizedPanx1 and Panx2 gap junction proteins in the lens is, therefore, ratherintriguing. Co-expression of pannexins and abundant connexins in thelens suggests that the two gap junction protein families have distinctroles in cell communication.Methods: Panx1 and Panx2 expression was studied by in situhybridization and quantitative RT-PCR. We examined properties and tissuedistribution of Panx1 isoforms by Western blot analysis.Immunohistochemistry was used to visualize lens regions that accumulatePanx1 to study intercellular localization and spatial relationship withlens connexin gap junctions.Results: Panx1 and Panx2 expression peaked in lens epithelial cellsprior to differentiation. We detected one ubiquitously expressed Panx1isoform and two additional isoforms that were only detected in the lensand the retina. Our results indicated that the ubiquitous 58 kDa and theoligomeric 120 kDa isoforms were plasma membrane-bound, resistant toTriton X-100 treatment, and was likely associated withcholesterol-enriched membrane microdomains. Immunohistochemistryrevealed Panx1-specific punctuate labeling in the plasma membrane, andintensive labeling of the organelles in the epithelial and immaturefiber cells. In addition, we detected Panx1 immunoreactivity in bloodendothelial cells of the tunica vasculosa lentis capillaries and inblood erythrocytes.Conclusions: Despite similarity in detergent solubility of pannexinsand connexins, the lack of spatial co-localization in the lens membranessuggested a distinct, non-redundant to connexin function for theseproteins in the membrane.

[学科分类] 生物化学/生物物理