QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 23 December 2002
doi: 10.1242/jcs.00267

This Article Figures Only Full Text Full Text (PDF) All Versions of this Article: jcs.00267v1 116/4/683    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wang, W.-J. Articles by Beers, M. F. Search for Related Content PubMed PubMed Citation Articles by Wang, W.-J. Articles by Beers, M. F.

Deletion of exon 4 from human surfactant protein C results in aggresome formation and generation of a dominant negative

Lung Epithelial Cell Biology Laboratories, Pulmonary and Critical Care Division, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA

^* Author for correspondence (e-mail: mfbeers{at}mail.med.upenn.edu)

Accepted 9 November 2002

Human surfactant protein C (hSP-C) is synthesized by the alveolar type 2 cell as a 197 amino acid integral membrane proprotein and proteolytically processed to a secreted 3.7 kDa mature form. Although the SP-C null mouse possesses a non-lethal phenotype, a heterozygous substitution of A for G in the first base of intron 4 of the human SP-C gene (c.460+1A>G) has been reported in association with familial interstitial lung disease and absence of mature protein. This mutation produces a splice deletion of exon 4 (Exon4) resulting in removal of a positionally conserved cysteine in the C-terminal flanking propeptide. Based on a prior study showing that an identical deletion in the rat isoform diverted mutant protein to stable aggregates, we hypothesized that expression of the Exon4 mutation would result in disruption of intracellular trafficking of both mutant and wild-type proSP-C. We tested this in vitro using fusion proteins of EGFP conjugated either to wild-type SP-C (EGFP/hSP-C^1-197) or to SP-C deleted of Exon4 (EGFP/hSP-C^Exon4). Fluorescence microscopy showed that EGFP/hSP-C^1-197 transfected into A549 cells was expressed in a punctuate pattern in CD63 (+) cytoplasmic vesicles, whereas EGFP/hSP-C^Exon4 accumulated in ubiquitinated perinuclear inclusions linked to the microtubule organizing center. A similar juxtanuclear pattern was observed following transfection of SP-C cDNA lacking only cysteine residues in the C-terminal propeptide encoded by Exon 4 (EGFP/hSP-C^C120/121G). To evaluate whether mutant proSP-C could function as a dominant negative, EGFP/hSP-C^Exon4 was cotransfected with HA-tagged hSP-C^1-197 and resulted in the restriction of both forms to perinuclear compartments. Addition of Na⁺ 4-phenylbutyrate, a facilitator of trafficking of other misfolded proteins, attenuated the aggregation of EGFP/hSP-C^Exon4. We conclude that c.460+1A>G mutation of human SP-C results in disruption of disulfide-mediated folding encoded by Exon 4 leading to diversion of unprocessed proSP-C to aggresomes. The heterotypic oligomerization of hSP-C^1-197 and hSP-C^Exon4 provides a molecular mechanism for the dominant-negative effect observed in vivo.

Key words: Surfactant Protein C, Interstitial lung disease, Protein trafficking, Aggresome, Conformational disease

This article has been cited by other articles:

				M. Korfei, C. Ruppert, P. Mahavadi, I. Henneke, P. Markart, M. Koch, G. Lang, L. Fink, R.-M. Bohle, W. Seeger, et al. Epithelial Endoplasmic Reticulum Stress and Apoptosis in Sporadic Idiopathic Pulmonary Fibrosis Am. J. Respir. Crit. Care Med., October 15, 2008; 178(8): 838 - 846. [Abstract] [Full Text] [PDF]

				W. A. Gower, S. E. Wert, and L. M. Nogee Inherited Surfactant Disorders NeoReviews, October 1, 2008; 9(10): e458 - e467. [Abstract] [Full Text] [PDF]

				M. Dong, J. P. Bridges, K. Apsley, Y. Xu, and T. E. Weaver ERdj4 and ERdj5 Are Required for Endoplasmic Reticulum-associated Protein Degradation of Misfolded Surfactant Protein C Mol. Biol. Cell, June 1, 2008; 19(6): 2620 - 2630. [Abstract] [Full Text] [PDF]

				S. Mulugeta, J. A. Maguire, J. L. Newitt, S. J. Russo, A. Kotorashvili, and M. F. Beers Misfolded BRICHOS SP-C mutant proteins induce apoptosis via caspase-4- and cytochrome c-related mechanisms Am J Physiol Lung Cell Mol Physiol, September 1, 2007; 293(3): L720 - L729. [Abstract] [Full Text] [PDF]

				H. Johansson, K. Nordling, T. E. Weaver, and J. Johansson The Brichos Domain-containing C-terminal Part of Pro-surfactant Protein C Binds to an Unfolded Poly-Val Transmembrane Segment J. Biol. Chem., July 28, 2006; 281(30): 21032 - 21039. [Abstract] [Full Text] [PDF]

				J. P. Bridges, Y. Xu, C.-L. Na, H. R. Wong, and T. E. Weaver Adaptation and increased susceptibility to infection associated with constitutive expression of misfolded SP-C J. Cell Biol., January 30, 2006; 172(3): 395 - 407. [Abstract] [Full Text] [PDF]

				S. Mulugeta, V. Nguyen, S. J. Russo, M. Muniswamy, and M. F. Beers A Surfactant Protein C Precursor Protein BRICHOS Domain Mutation Causes Endoplasmic Reticulum Stress, Proteasome Dysfunction, and Caspase 3 Activation Am. J. Respir. Cell Mol. Biol., June 1, 2005; 32(6): 521 - 530. [Abstract] [Full Text] [PDF]

				J. C. Grutters and R. M. du Bois Genetics of fibrosing lung diseases Eur. Respir. J., May 1, 2005; 25(5): 915 - 927. [Abstract] [Full Text] [PDF]

				F. Brasch, M. Griese, M. Tredano, G. Johnen, M. Ochs, C. Rieger, S. Mulugeta, K.M. Muller, M. Bahuau, and M.F. Beers Interstitial lung disease in a baby with a de novo mutation in the SFTPC gene Eur. Respir. J., July 1, 2004; 24(1): 30 - 39. [Abstract] [Full Text] [PDF]

				A. Hamvas, L. M. Nogee, F. V. White, P. Schuler, B. P. Hackett, C. B. Huddleston, E. N. Mendeloff, F.-F. Hsu, S. E. Wert, L. W. Gonzales, et al. Progressive Lung Disease and Surfactant Dysfunction with a Deletion in Surfactant Protein C Gene Am. J. Respir. Cell Mol. Biol., June 1, 2004; 30(6): 771 - 776. [Abstract] [Full Text] [PDF]

				S. M. Noorwez, R. Malhotra, J. H. McDowell, K. A. Smith, M. P. Krebs, and S. Kaushal Retinoids Assist the Cellular Folding of the Autosomal Dominant Retinitis Pigmentosa Opsin Mutant P23H J. Biol. Chem., April 16, 2004; 279(16): 16278 - 16284. [Abstract] [Full Text] [PDF]

				J. P. Bridges, S. E. Wert, L. M. Nogee, and T. E. Weaver Expression of a Human Surfactant Protein C Mutation Associated with Interstitial Lung Disease Disrupts Lung Development in Transgenic Mice J. Biol. Chem., December 26, 2003; 278(52): 52739 - 52746. [Abstract] [Full Text] [PDF]

				S. Mulugeta and M. F. Beers Processing of Surfactant Protein C Requires a Type II Transmembrane Topology Directed by Juxtamembrane Positively Charged Residues J. Biol. Chem., November 28, 2003; 278(48): 47979 - 47986. [Abstract] [Full Text] [PDF]