What Causes Psoriasis? Keratin Hyperkeratosis

Today, we will delve into keratin, a topic within the broader subject of psoriasis. Keratin is one of the components that make up the cytoskeleton. The cytoskeleton refers to the components used by cells to maintain their three-dimensional shape and structure. It can be likened to the way rebar and cement form the framework when constructing a building.

Components of the Cytoskeleton

The components that make up the cytoskeleton are broadly divided into three types: microtubule, actin filament, and intermediate filament. Among these, keratin is what corresponds to the intermediate filament.

Keratin is frequently used as a major component of the cytoskeleton in mammals. Making Sense of the Epithelial Barrier: What Molecular Biology and Genetics Tell Us About the Functions of Oral Mucosal and Epidermal Tissues

As you can see in the image above, keratin filaments within basal epithelial cells extend in all directions like tent poles, playing a role in maintaining the cell's shape. These keratins connect cells to adjacent cells via desmosome junctions in the cell junction region, forming a physically rigid structure. This is similar to connecting LEGO bricks to create a strong structure.

The Existence of Diverse Keratins

Numerous types of keratins exist. In mammals, over 50 different types of keratins are utilized. Keratins are distinguished by numbers, and different keratins are expressed depending on the cell's location or function, determining the cell's role and shape.

Keratins such as K31, K35, K81, K85, and K86 are primarily used in hair, while K1, K2, K5, K9, K10, and K14 are used in the epidermis. Thus, different keratins are expressed and function in different tissues and cells.

Oral Mucosa and Keratin

In the oral mucosa, different keratins are used compared to the epidermis. The mucosa lacks a stratum corneum (SC), and the keratin types used in the superficial layer are also different, namely K4 and K13.

Zhang, L. (2018). Keratins in Skin Epidermal Development and Diseases. Keratin.

Keratin in the Epidermis

The epidermal layer is divided into the basal layer, spinous layer, granular layer, and stratum corneum. In the basal layer, K14 is primarily used. K10 keratin can also be present in the basal layer, but it is predominantly used in the spinous layer, granular layer, and stratum corneum. This is a result of different keratins being expressed to differentiate cell functions.

Keratin Mutations and Diseases

If there are issues in the keratin expression process in the epidermis, blistering and inflammatory diseases can arise due to K14 gene mutations. Conversely, mutations in K10 can lead to conditions such as hyperkeratosis. In psoriasis, changes in K10 result in the appearance of keratins such as K16 and K17.

Differences in Keratin and Psoriasis

In psoriasis, hyperkeratosis and changes in epidermal thickness are observed. These changes are related to alterations in the type of keratin originally used.

Differential Evolution of the Epidermal Keratin Cytoskeleton in Terrestrial and Aquatic Mammals

In the epidermal layer of a typical person, K5, K14, K1, and K10 are primarily used. However, in conditions like psoriasis, K6, K16, and K17 are used, which are keratins predominantly found in the thick epidermis of dolphins.

In summary, hyperkeratosis and changes in epidermal thickness are observed in psoriasis, which are associated with alterations in keratin composition.