Pannexin1 channels contain a glycosylation site that targets the hexamer to the plasma membrane.
Pannexins are newly discovered channel proteins expressed in many different tissues and abundantly in the vertebrate central nervous system. Based on membrane topology, folding and secondary structure prediction, pannexins are proposed to form gap junction-like structures. We show here that Pannexin1 forms a hexameric channel and reaches the cell surface but, unlike connexins, is N-glycosylated. Using site-directed mutagenesis we analyzed three putative N-linked glycosylation sites and examined the effects of each mutation on channel expression. We show for the first time that Pannexin1 is glycosylated at Asn-254 and that this residue is important for plasma membrane targeting. The glycosylation of Pannexin1 at its extracellular surface makes it unlikely that two oligomers could dock to form an intercellular channel. Ultrastructural analysis by electron microscopy confirmed that Pannexin1 junctional areas do not appear as canonical gap junctions. Rather, Pannexin1 channels are distributed throughout the plasma membrane. We propose that N-glycosylation of Pannexin1 could be a significant mechanism for regulating the trafficking of these membrane proteins to the cell surface in different tissues.
Boassa
Daniela
D
National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, Department of Neurosciences, University of California, San Diego, La Jolla, California 92093-0608, USA. dboassa@gmail.com
Ambrosi
Cinzia
C
Qiu
Feng
F
Dahl
Gerhard
G
Gaietta
Guido
G
Sosinsky
Gina
G
D001216:Asparagine / Q000378:metabolism; D019921:Biotinylation; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D017630:Connexins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006031:Glycosylation; D006801:Humans; D007150:Immunohistochemistry; D007473:Ion Channels / Q000648:ultrastructure*; D007668:Kidney / Q000166:cytology; D008954:Models, Biological; D009154:Mutation; D009419:Nerve Tissue Proteins; D011499:Protein Processing, Post-Translational; D017433:Protein Structure, Secondary; D013388:Succinimides / Q000494:pharmacology
D017630:Connexins; D003432:Cross-Linking Reagents; D007473:Ion Channels; D009419:Nerve Tissue Proteins; C492764:PANX1 protein, human; D013388:Succinimides; D001216:Asparagine; C011240:dithiobis(succinimidylpropionate)