CTNS cotransports CySS-, H+ from lysosomal lumen to cytosol

Stable Identifier
Reaction [transition]
Homo sapiens
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Cystinosin (CTNS) is an integral lysosomal membrane protein which can transport L-cystine (CySS-, the oxidative product of two cysteine molecules linked via a disulfide bond) together with H+ out of lysosomes. CySS- is a component of hair, skin and nails. Defects in CTNS cause cystinosis, lysosomal storage-type diseases due to defective transport of CySS- across the lysosomal membrane (Town et al. 1998, Anikster et al. 1999; review Elmonem et al. 2016). Patients with cystinosis frequently exhibit blond hair and a fair complexion, suggesting an involvement in melanogenesis. Chiaverini et al. show CTNS is also localised to melanosomes. CTNS silencing led to a 75% reduction of melanin synthesis, caused by a degradation of tyrosinase (the enzyme responsible for melanin biosynthesis), thereby identifying a role for CTNS in melanogenesis (Chiaverini et al. 2012).
Literature References
PubMed ID Title Journal Year
27102039 Cystinosis: a review

Veys, KR, van den Heuvel, LP, Levtchenko, E, Soliman, NA, van Dyck, M, Elmonem, MA

Orphanet J Rare Dis 2016
10571941 CTNS mutations in patients with cystinosis

Anikster, Y, Shotelersuk, V, Gahl, WA

Hum. Mutat. 1999
9537412 A novel gene encoding an integral membrane protein is mutated in nephropathic cystinosis

Attard, M, Bates, GP, Whitmore, SA, Cherqui, S, Callen, DF, van't Hoff, W, Town, M, Gribouval, O, Jean, G, Antignac, C, Broyer, M, Forestier, L

Nat. Genet. 1998
22649030 Cystinosin is a melanosomal protein that regulates melanin synthesis

Picardo, M, Flori, E, Berard, E, Antignac, C, Cochat, P, Fontas, E, Bernard, FX, Sillard, L, Guest, G, Ortonne, JP, Briganti, S, Wakamatsu, K, Cailliez, M, Chiaverini, C, Foulard, M, Ito, S, Ballotti, R, Niaudet, P

FASEB J. 2012
Catalyst Activity

L-cystine transmembrane transporter activity of CTNS [lysosomal membrane]

Orthologous Events
Cross References
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