title: Pannexin 1 and pannexin 3 are glycoproteins that exhibit many distinct characteristics from the connexin family of gap junction proteins.
abstract: Pannexins are mammalian orthologs of the invertebrate gap junction proteins innexins and thus have been proposed to play a role in gap junctional intercellular communication. Localization of exogenously expressed pannexin 1 (Panx1) and pannexin 3 (Panx3), together with pharmacological studies, revealed a cell surface distribution profile and life cycle dynamics that were distinct from connexin 43 (Cx43, encoded by Gja1). Furthermore, N-glycosidase treatment showed that both Panx1 (approximately 41-48 kD species) and Panx3 (approximately 43 kD) were glycosylated, whereas N-linked glycosylation-defective mutants exhibited a decreased ability to be transported to the cell surface. Tissue surveys revealed the expression of Panx1 in several murine tissues--including in cartilage, skin, spleen and brain--whereas Panx3 expression was prevalent in skin and cartilage with a second higher-molecular-weight species present in a broad range of tissues. Tissue-specific localization patterns of Panx1 and Panx3 ranging from distinct cell surface clusters to intracellular profiles were revealed by immunostaining of skin and spleen sections. Finally, functional assays in cultured cells transiently expressing Panx1 and Panx3 were incapable of forming intercellular channels, but assembled into functional cell surface channels. Collectively, these studies show that Panx1 and Panx3 have many characteristics that are distinct from Cx43 and that these proteins probably play an important biological role as single membrane channels.
authors.affiliation: Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, N6A 5C1, Canada.
authors.forename: Silvia
authors.initials: S
authors.lastname: Penuela
authors.forename: Ruchi
authors.initials: R
authors.lastname: Bhalla
authors.forename: Xiang-Qun
authors.initials: XQ
authors.lastname: Gong
authors.forename: Kyle N
authors.initials: KN
authors.lastname: Cowan
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Celetti
authors.forename: Bryce J
authors.initials: BJ
authors.lastname: Cowan
authors.forename: Donglin
authors.initials: D
authors.lastname: Bai
authors.forename: Qing
authors.initials: Q
authors.lastname: Shao
authors.forename: Dale W
authors.initials: DW
authors.lastname: Laird
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D017629:Gap Junctions / Q000737:chemistry / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D012867:Skin / Q000166:cytology / Q000378:metabolism; D013154:Spleen / Q000166:cytology / Q000378:metabolism
chemical_list: D018031:Connexin 43; D017630:Connexins; D006023:Glycoproteins; D009419:Nerve Tissue Proteins; C492764:PANX1 protein, human; C492766:PANX3 protein, human; C503631:Panx1 protein, mouse; D011993:Recombinant Fusion Proteins; C528477:pannexin 3 protein, mouse