Large ribosomal subunit protein eL21

RPL21 encodes the large ribosomal subunit protein eL21, a structural component of the ribosome essential for protein synthesis (UniProt: P46778). The protein is part of the large ribonucleoprotein complex responsible for translating mRNA into polypeptides across all cellular contexts.

RPL21 is broadly expressed and primarily associated with ribosomal function. UniProt records a genetic disease association with Hypotrichosis 12 (HYPT12, MIM 615885), an autosomal dominant condition involving progressive hair loss and abnormal hair follicle development, but no major tissue-specific localization is noted beyond its ubiquitous ribosomal role.

In Alzheimer's Disease, RPL21 shows reduced abundance in post-mortem AD brain relative to age-matched controls (Chaparral AD proteomics). The protein was significantly downregulated with a mean log2 fold-change of −0.44 in a TMT-labeled proteomics analysis across subcellular fractions. This reduction may reflect impaired protein synthesis capacity in AD pathology, though the functional consequence of decreased ribosomal protein levels in neurodegeneration requires further investigation.