Functional characterization of a naturally occurring Cx50 truncation.
نویسندگان
چکیده
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.
منابع مشابه
Bacterial Expression and Functional Characterization of A Naturally Occurring Exon6-less Preprochymosin cDNA
Chymosin (Rennin EC 3.4.23.4), an aspartyl proteinase, is the major proteolytic enzyme in the fourthstomach of the unweaned calf, and it is formed by proteolytic activation of its zymogene, prochymosin.Following the cloning of synthesized cDNAs on mRNA pools extracted from the mucosa of the calf fourthstomach, we have identified an alternatively spliced form of preprochymosin ...
متن کاملSelective interactions among the multiple connexin proteins expressed in the vertebrate lens: the second extracellular domain is a determinant of compatibility between connexins
Gap junctions are collections of intercellular channels composed of structural proteins called connexins (Cx). We have examined the functional interactions of the three rodent connexins present in the lens, Cx43, Cx46, and Cx50, by expressing them in paired Xenopus oocytes. Homotypic channels containing Cx43, Cx46, or Cx50 all developed high conductance. heterotypic channels composed of Cx46 pa...
متن کاملOptimal lens epithelial cell proliferation is dependent on the connexin isoform providing gap junctional coupling.
PURPOSE Gap junctions between epithelial cells are essential for normal lens growth. In mice, knockout of Cx50 or targeted replacement of Cx50 with Cx46 (knockin) caused smaller lenses because of decreased epithelial cell proliferation. However, it remains unclear whether Cx50 functionally contributes to lens epithelial coupling during maximal proliferation on postnatal day 2 (P2) and P3. To de...
متن کاملThe cataract-inducing S50P mutation in Cx50 dominantly alters the channel gating of wild-type lens connexins.
Mutations within connexin50 (Cx50) have been linked to various cataract phenotypes. To determine the mechanism behind cataract formation we used the paired Xenopus oocyte system in conjunction with transfected HeLa cells and genetically engineered mouse models to examine the functional characteristics of gap junctions in which a cataract-causing mutant of Cx50 (hereafter referred to as Cx50-S50...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Investigative ophthalmology & visual science
دوره 47 10 شماره
صفحات -
تاریخ انتشار 2006