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Vol. 16, Issue 3, 1427-1438, March 2005

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Defining the Properties of the Nonhelical Tail Domain in Type II Keratin 5: Insight from a Bullous Disease-causing Mutation

Departments of Biological Chemistry and Dermatology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205

Submitted June 18, 2004; Accepted January 3, 2005
Monitoring Editor: Thomas Pollard

Inherited mutations in the intermediate filament (IF) proteins keratin 5 (K5) or keratin 14 (K14) cause epidermolysis bullosa simplex (EBS), in which basal layer keratinocytes rupture upon trauma to the epidermis. Most mutations are missense alleles affecting amino acids located in the central -helical rod domain of K5 and K14. Here, we study the properties of an unusual EBS-causing mutation in which a nucleotide deletion (1649delG) alters the last 41 amino acids and adds 35 residues to the C terminus of K5. Relative to wild type, filaments coassembled in vitro from purified K5-1649delG and K14 proteins are shorter and exhibit weak viscoelastic properties when placed under strain. Loss of the C-terminal 41 residues contributes to these alterations. When transfected in cultured epithelial cells, K5-1649delG incorporates into preexisting keratin IFs and also forms multiple small aggregates that often colocalize with hsp70 in the cytoplasm. Aggregation is purely a function of the K5-1649delG tail domain; in contrast, the cloned 109 residue-long tail domain from wild type K5 is distributed throughout the cytoplasm and colocalizes partly with keratin IFs. These data provide a mechanistic basis for the cell fragility seen in individuals bearing the K5-1649delG allele, and point to the role of the C-terminal 41 residues in determining K5's assembly properties.

Address correspondence to: Pierre A. Coulombe (coulombe{at}jhmi.edu).

This article has been cited by other articles:

				L.-H. Gu and P. A. Coulombe Hedgehog Signaling, Keratin 6 Induction, and Sebaceous Gland Morphogenesis: Implications for Pachyonychia Congenita and Related Conditions Am. J. Pathol., September 1, 2008; 173(3): 752 - 761. [Abstract] [Full Text] [PDF]

				S. Kim and P. A. Coulombe Intermediate filament scaffolds fulfill mechanical, organizational, and signaling functions in the cytoplasm Genes & Dev., July 1, 2007; 21(13): 1581 - 1597. [Abstract] [Full Text] [PDF]