Last updated on: 05.05.2022

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General information
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The proteasome is a 1,700 kDa protein complex that is found in the cytoplasm and also in the nucleus of eukaryotes. As a component of protein quality control, the proteasome degrades proteins into fragments. The enzyme complex belongs to the proteases(peptidases).

The proteasome in eukaryotes consists of one 20S and two 19S subunits, which in turn are composed of several proteins. In eukaryotes, the 19S complexes sit cap-like on the two openings of the 20S complex, a tube-like hollow structure.

Both caps regulate access to the 20S complex. They recognize proteins destined for degradation, label them with a polyubiquitin chain in a multi-step enzymatic process using ubiquitin-protein ligases. The proteins labelled and unfolded in this way now fit into the 20S complex. There they are enzymatically degraded. Ubiquitin is a small protein with a molecular mass of 8.5 kDa.

Protein degradation is vital for the cell. Thus, metabolic enzymes, transcription factors or proteins regulating the cell cycle such as cyclins, CDK inhibitors are degraded. Likewise, defective proteins are degraded (garbage can principle).

POMP and psoriasis: It is known that the ubiquitin-proteasome pathway is involved in the pathogenesis of psoriasis. The proteasome subunits (20S and 26S) are increased in psoriatic skin.POMP binds to 20S precursor complexes and is overexpressed in lesional epidermal psoriatic skin. Knockdown of POMP inhibited proliferation of HaCaT cells and induced apoptosis by inhibiting proteasome assembly. Partial deletion of POMP inhibits the expression of the differentiation markers keratin 10 and involucrin during [Ca2+]-induced HaCaT cell differentiation (Zieba BA et al. 2017).

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  1. Dahlqvist J et al (2010) A single-nucleotide deletion in the POMP 5' UTR causes a transcriptional switch and altered epidermal proteasome distribution in KLICK genodermatosis. Am J Hum Genet 86:596-603.
  2. Takeichi Tet al. (2020) KLICK Syndrome Linked to a POMP Mutation Has Features Suggestive of an Autoinflammatory Keratinization Disease. Front Immunol 11:641.
  3. Zieba BA et al. (2017) The proteasome maturation protein POMP increases proteasome assembly and activity in psoriatic lesional skin. J Dermatol Sci 88:10-19.

Last updated on: 05.05.2022