title: The carboxyl tail of connexin32 regulates gap junction assembly in human prostate and pancreatic cancer cells.
abstract: Connexins, the constituent proteins of gap junctions, are transmembrane proteins. A connexin (Cx) traverses the membrane four times and has one intracellular and two extracellular loops with the amino and carboxyl termini facing the cytoplasm. The transmembrane and the extracellular loop domains are highly conserved among different Cxs, whereas the carboxyl termini, often called the cytoplasmic tails, are highly divergent. We have explored the role of the cytoplasmic tail of Cx32, a Cx expressed in polarized and differentiated cells, in regulating gap junction assembly. Our results demonstrate that compared with the full-length Cx32, the cytoplasmic tail-deleted Cx32 is assembled into small gap junctions in human pancreatic and prostatic cancer cells. Our results further document that the expression of the full-length Cx32 in cells, which express the tail-deleted Cx32, increases the size of gap junctions, whereas the expression of the tail-deleted Cx32 in cells, which express the full-length Cx32, has the opposite effect. Moreover, we show that the tail is required for the clustering of cell-cell channels and that in cells expressing the tail-deleted Cx32, the expression of cell surface-targeted cytoplasmic tail alone is sufficient to enhance the size of gap junctions. Our live-cell imaging data further demonstrate that gap junctions formed of the tail-deleted Cx32 are highly mobile compared with those formed of full-length Cx32. Our results suggest that the cytoplasmic tail of Cx32 is not required to initiate the assembly of gap junctions but for their subsequent growth and stability. Our findings suggest that the cytoplasmic tail of Cx32 may be involved in regulating the permeability of gap junctions by regulating their size.
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: Parul
authors.initials: P
authors.lastname: Katoch
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: Shalini
authors.initials: S
authors.lastname: Mitra
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: Anuttoma
authors.initials: A
authors.lastname: Ray
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: Linda
authors.initials: L
authors.lastname: Kelsey
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: Brett J
authors.initials: BJ
authors.lastname: Roberts
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: James K
authors.initials: JK
authors.lastname: Wahl
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: Keith R
authors.initials: KR
authors.lastname: Johnson
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Department of Oral Biology, Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198. Electronic address: pmehta@unmc.edu.
authors.forename: Parmender P
authors.initials: PP
authors.lastname: Mehta
mesh_terms: D045744:Cell Line, Tumor; D017630:Connexins / Q000096:biosynthesis* / Q000235:genetics; D017629:Gap Junctions / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010539:Permeability; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D017434:Protein Structure, Tertiary; D000097002:Gap Junction beta-1 Protein
chemical_list: D017630:Connexins; D009363:Neoplasm Proteins; D000097002:Gap Junction beta-1 Protein
keywords: Cell Adhesion; Cell junction; Connexin; Gap Junction; Gap Junctions; Protein Assembly