| First Author | DeRosa AM | Year | 2006 |
| Journal | Invest Ophthalmol Vis Sci | Volume | 47 |
| Issue | 10 | Pages | 4474-81 |
| PubMed ID | 17003442 | Mgi Jnum | J:116271 |
| Mgi Id | MGI:3693410 | Doi | 10.1167/iovs.05-1582 |
| Citation | DeRosa AM, et al. (2006) Functional characterization of a naturally occurring Cx50 truncation. Invest Ophthalmol Vis Sci 47(10):4474-81 |
| abstractText | PURPOSE: Lens connexins undergo proteolytic cleavage of their C termini during fiber maturation. Although the functional significance of this is unknown, cleavage has been correlated with changes in channel-gating properties. This study evaluates the functional consequences of this endogenous truncation by characterizing the properties of a C-terminal truncated Cx50 protein. METHODS: Murine and human Cx50 were truncated at amino acids 290 and 294, respectively, before expression in paired Xenopus oocytes or mammalian cells. Protein expression was evaluated by immunocytochemistry. Dual whole-cell voltage clamp techniques were used to analyze macroscopic and single-channel conductance, voltage-gating properties, and kinetics; pH gating sensitivity was measured by superfusion with 100% CO2-saturated media. RESULTS: Cx50tr290 channels exhibited an 86% to 89% reduction in mean macroscopic conductance compared with full-length Cx50. Heterotypic channels formed functional gap junctions, displayed an intermediate level of coupling, and exhibited unaltered voltage-gating properties. C-terminal truncation did not alter single-channel gating characteristics or unitary conductance. Interestingly, truncated and full-length Cx50 channel conductances were reversibly blocked by cytoplasmic acidification. CONCLUSIONS: C-terminal truncation of Cx50 did not inhibit the formation of homotypic or heterotypic channels. However, a significant decrease in conductance was observed for truncated channels, a phenomenon independent of alterations in voltage-gating sensitivity, kinetics, or chemical gating. These results provide a plausible explanation for the 50% decrease in junctional coupling observed during lens fiber maturation. |
