Cysteine and tyrosine-rich protein 1 (CYYR1)

Cysteine and tyrosine-rich protein 1 (CYYR1) is a highly conserved, single-pass type I transmembrane protein encoded by the *CYYR1* gene on human chromosome 21q21.2[5]. Its defining feature is a central domain rich in cysteine and tyrosine residues, with three C-terminal Pro–Pro–x–Tyr (PPxY or PY) motifs. These motifs enable CYYR1 to interact with WW domain-containing E3 ubiquitin ligases, such as WWP1, targeting them for lysosomal degradation via autoubiquitination and recruitment to late endosomal vesicles, in complex with adaptors like ANKRD13A[2][3]. CYYR1 is predominantly expressed in the diffuse neuroendocrine system and has splice variants. While its precise physiological role remains incompletely defined, CYYR1 modulates membrane protein trafficking and may regulate cellular antioxidant levels through effects on glutathione uptake. In cancer biology, reduced expression of CYYR1 is correlated with worse prognosis in breast cancer, suggesting a possible tumor suppressor function related to limiting WWP1-dependent oncogenic signaling[2][3][1][5]. To date, there are no known drugs targeting CYYR1 directly, nor documented safety concerns specific to this protein.

Other names

C21orf95cysteine/tyrosine-rich 1proline-rich domain-containing protein