The University of Southampton
University of Southampton Institutional Repository

Occludin TM4(-): an isoform of the tight junction protein present in primates lacking the fourth transmembrane domain

Occludin TM4(-): an isoform of the tight junction protein present in primates lacking the fourth transmembrane domain
Occludin TM4(-): an isoform of the tight junction protein present in primates lacking the fourth transmembrane domain
The tight junction protein occludin possesses four transmembrane domains, two extracellular loops, and cytoplasmic N- and C-termini. Reverse transcription-PCR analysis of human tissues, embryos and cells using primers spanning the fourth transmembrane domain (TM4) and adjacent C-terminal region revealed two products. The larger and predominant product corresponded in sequence to canonical occludin (TM4+), while the smaller product exhibited a 162 bp deletion encoding the entire TM4 and immediate C-terminal flanking region (TM4-). Examination of the genomic occludin sequence identified that the 162 bp sequence deleted in TM4- coincided precisely with occludin exon 4, strongly suggesting that TM4- is an alternative splice isoform generated by skipping of exon 4. Indeed, the reading frame of downstream exons is not affected by exclusion of exon 4.
The presence of both TM4+ and TM4- occludin isoforms was also identified in monkey epithelial cells but TM4- was undetected in murine and canine tissue and cells, indicating a late evolutionary origin for this alternative splicing event. Conceptual translation of TM4- isoform predicts extracellular localisation of the C-terminus. Immunocytochemical processing of living human Caco-2 cells using a C-terminal occludin antibody revealed weak, discontinuous staining restricted to the periphery of subconfluent islands of cells, or islands generated by wounding confluent layers. In occludin immunoblots, a weak band at 58 kDa, smaller than the predominant band at 65 kDa and corresponding to the predicted mass of TM4- isoform, is evident and upregulated in subconfluent cells. These data suggest that the TM4- isoform may be translated at low levels in specific conditions and may contribute to regulation of occludin function.
occludin, tight junction, epithelium, isoform alternative splicing, embryo
0021-9533
3171-3180
Ghassemifar, M.R.
219dba14-d37d-4062-b687-bcdcc6889045
Sheth, Bhavwanti
2ca6ed58-a992-47b7-b3a5-3c5df82aada7
Papenbrock, T.
ff77ce9c-910b-4e64-ac29-7a2cdcd52d48
Leese, H.J.
1f369c23-4361-4534-a093-54699ec5eceb
Houghton, Franchesca D.
53946041-127e-45a8-9edb-bf4b3c23005f
Fleming, T.P.
1431b2dc-b145-4bc2-aea4-bc360fc370e9
Ghassemifar, M.R.
219dba14-d37d-4062-b687-bcdcc6889045
Sheth, Bhavwanti
2ca6ed58-a992-47b7-b3a5-3c5df82aada7
Papenbrock, T.
ff77ce9c-910b-4e64-ac29-7a2cdcd52d48
Leese, H.J.
1f369c23-4361-4534-a093-54699ec5eceb
Houghton, Franchesca D.
53946041-127e-45a8-9edb-bf4b3c23005f
Fleming, T.P.
1431b2dc-b145-4bc2-aea4-bc360fc370e9

Ghassemifar, M.R., Sheth, Bhavwanti, Papenbrock, T., Leese, H.J., Houghton, Franchesca D. and Fleming, T.P. (2002) Occludin TM4(-): an isoform of the tight junction protein present in primates lacking the fourth transmembrane domain. Journal of Cell Science, 115 (15), 3171-3180. (doi:10.1242/jcs.115.15.3171).

Record type: Article

Abstract

The tight junction protein occludin possesses four transmembrane domains, two extracellular loops, and cytoplasmic N- and C-termini. Reverse transcription-PCR analysis of human tissues, embryos and cells using primers spanning the fourth transmembrane domain (TM4) and adjacent C-terminal region revealed two products. The larger and predominant product corresponded in sequence to canonical occludin (TM4+), while the smaller product exhibited a 162 bp deletion encoding the entire TM4 and immediate C-terminal flanking region (TM4-). Examination of the genomic occludin sequence identified that the 162 bp sequence deleted in TM4- coincided precisely with occludin exon 4, strongly suggesting that TM4- is an alternative splice isoform generated by skipping of exon 4. Indeed, the reading frame of downstream exons is not affected by exclusion of exon 4.
The presence of both TM4+ and TM4- occludin isoforms was also identified in monkey epithelial cells but TM4- was undetected in murine and canine tissue and cells, indicating a late evolutionary origin for this alternative splicing event. Conceptual translation of TM4- isoform predicts extracellular localisation of the C-terminus. Immunocytochemical processing of living human Caco-2 cells using a C-terminal occludin antibody revealed weak, discontinuous staining restricted to the periphery of subconfluent islands of cells, or islands generated by wounding confluent layers. In occludin immunoblots, a weak band at 58 kDa, smaller than the predominant band at 65 kDa and corresponding to the predicted mass of TM4- isoform, is evident and upregulated in subconfluent cells. These data suggest that the TM4- isoform may be translated at low levels in specific conditions and may contribute to regulation of occludin function.

Text
3171.pdf - Version of Record
Restricted to Repository staff only
Request a copy

More information

Published date: 1 August 2002
Additional Information: All the work for this paper took place within my laboratory and funded by my grants (Tom Fleming)
Keywords: occludin, tight junction, epithelium, isoform alternative splicing, embryo

Identifiers

Local EPrints ID: 24590
URI: http://eprints.soton.ac.uk/id/eprint/24590
ISSN: 0021-9533
PURE UUID: 781f7213-b873-4300-beb2-13428f1e7775
ORCID for Franchesca D. Houghton: ORCID iD orcid.org/0000-0002-5167-1694

Catalogue record

Date deposited: 31 Mar 2006
Last modified: 16 Mar 2024 03:49

Export record

Altmetrics

Contributors

Author: M.R. Ghassemifar
Author: Bhavwanti Sheth
Author: T. Papenbrock
Author: H.J. Leese
Author: T.P. Fleming

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×