Importance of molecular configuration in gap junctional permeability.
Gap junctions between insect oocytes and follicular epithelial cells allow transit of elongate Ca(2+)-binding proteins Calmodulin (CaM, 17 kDa) and Troponin-C (Trop-C, 18 kDa), but not multi-branched dextran (10 kDa) nor the Ca(2+)-binding protein Osteocalcin (Osteo, 6 kDa). By microinjection of fluorescently labeled versions of each of these molecules we were able to obtain visual evidence that, despite their lesser molecular weight, molecules with greater cross-sections were unable to transit these gap junctions, while heavier but elongate molecules could. While CaM had previously been shown to pass through gap junctions from oocytes to their surrounding epithelial cells, the ability of CaM and Trop-C to transit the gap junctions between adjacent epithelial cells had not been demonstrated. Evidence shown here demonstrates that the homologous gap junctions among epithelial cells, like the heterologous gap junctions between epithelial cells and the oocyte they surround, allow transit of elongate molecules up to at least 18 kDa. Furthermore, the evidence for four different molecules of differing molecular weights and configurations supports the hypothesis that it is molecular configuration, not chemical activity, that primarily determines the observed permeability of gap junctions to molecules 5-6 times larger than the molecular weight limit previously acknowledged.
Cieniewicz
Anne M
AM
Department of Biology, West Chester University, West Chester, PA 19383, United States.
Woodruff
Richard I
RI
D000818:Animals; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005260:Female; D017629:Gap Junctions / Q000378:metabolism*; D020062:Heteroptera / Q000378:metabolism*; D019476:Insect Proteins / Q000737:chemistry* / Q000378:metabolism; D008845:Microinjections; D008968:Molecular Conformation; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D010539:Permeability; D021381:Protein Transport
D019476:Insect Proteins