KRT5

KRT5 Full Name

keratin 5

KRT5 Introduction

The KRT5 gene provides instructions for producing keratin 5, a type II cytoskeletal keratin that serves as a fundamental structural protein in epithelial cells. Keratins are a family of tough, fibrous proteins that form the intricate structural framework of cells in the skin, hair, and nails. As a member of the type II cytokeratin family, keratin 5 is specifically expressed in the basal layer of the epidermis, where it partners with its type I partner, keratin 14, to create a resilient cytoskeletal network. This gene has garnered significant clinical attention because mutations in KRT5 are responsible for a spectrum of inherited skin disorders, most notably epidermolysis bullosa simplex and Dowling-Degos disease, highlighting its essential role in maintaining skin integrity and pigmentation.

Figure 1. Keratin filaments: structure, organization, and expression in the interfollicular epidermis. ( Coulombe P A, Lee C H. 2012)

Tissue Distribution and Cellular Localization
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KRT5 exhibits a highly specific expression pattern that is essentially restricted to stratified epithelial tissues. The gene shows biased expression in skin (with RPKM values of 2610.9) and esophagus (1766.7), reflecting its critical role in these tissues. Within the epidermis, KRT5 is specifically expressed in the basal layer, where proliferative keratinocytes reside. At the cellular level, keratin 5 localizes to the cytoplasm where it assembles into keratin intermediate filaments—a network of protein fibers that extends from the nucleus to the cell membrane. This cytoskeletal framework is particularly prominent in keratinocytes, where it provides mechanical integrity. The protein is also detected in the cornified envelope and plasma membrane, and is found in extracellular exosomes, suggesting potential roles in intercellular communication. In addition to skin and esophagus, KRT5 expression is observed in the urothelium of the bladder and ureter, where it specifically marks basal cells but not intermediate or superficial cell layers.

Emerging Role in Cancer and Other Diseases
While KRT5 is not classified as a classic cancer gene in the Cancer Gene Census, it has emerged as a valuable diagnostic and prognostic biomarker in several malignancies. In breast cancer, KRT5 expression characterizes the basal-like subtype, which is often associated with more aggressive behavior and triple-negative status. Cytokeratin 5 immunohistochemistry is routinely used in clinical pathology to subtype breast cancers and guide treatment decisions. In bladder cancer, KRT5 expression patterns help distinguish tumor subtypes and may predict clinical behavior. Studies have identified KRT5 as a biomarker of urinary bladder cancer in rat models, with human relevance under investigation. KRT5 expression in pT1 bladder cancer predicts intravesical recurrence in patients treated with bacillus Calmette-Guérin (BCG) instillation.

Alternate Names for KRT5

KRT5; keratin 5; K5; CK5; Tfip8; Krt2-5; AW146334; 3300001P10Rik; keratin, type II cytoskeletal 5; CK-5; krt5; keratin-5; cytokeratin 5; cytokeratin-5; 58 kDa cytokeratin; type-II keratin Kb5; tuftelin interacting protein 8; keratin complex 2, basic, gene 5; K5; CK5; DDD; DDD1; EBS2; KRT5A

• Immunohistochemistry Antibodies for Pathology
• Immunohistochemistry Antibodies for Pathology