Cysteine--tRNA ligase, cytoplasmic

Cysteine–tRNA ligase, cytoplasmic (CARS1) is an aminoacyl-tRNA synthetase that catalyzes the ATP-dependent ligation of cysteine to tRNA(Cys), an essential step in protein synthesis (UniProt: P49589). The enzyme is broadly expressed in human tissues and participates in fundamental translational mechanisms required for cellular protein production.

CARS1 is associated with microcephaly, developmental delay, and brittle hair syndrome (MDBH; MIM 618891), an autosomal recessive disorder marked by cognitive and motor impairment, structural hair abnormalities, and growth deficiency (UniProt: P49589). These disease associations underscore the critical role of accurate cysteine incorporation in human development and cellular integrity.

In Alzheimer's disease, CARS1 is upregulated in post-mortem AD brain tissue relative to age-matched controls (Chaparral AD proteomics). The protein showed increased abundance with a mean log₂ fold-change of 0.68 across analyzed subcellular fractions in a TMT-labeled quantitative proteomics experiment. This upregulation may reflect altered translational demand or proteostatic stress in the AD brain.