The human OCTN1 (SLC22A4) reconstituted in liposomes catalyzes acetylcholine transport which is defective in the mutant L503F associated to the Crohn's disease

Giovambattista Pani, Lorena Pochini, Mariafrancesca Scalise, Michele Galluccio, Katherine A. Siminovitch, Cesare Indiveri

Risultato della ricerca: Contributo in rivistaArticolo in rivistapeer review

40 Citazioni (Scopus)

Abstract

The organic cation transporter (OCTN1) plays key roles in transport of selected organic cations, but understanding of its biological functions remains limited by restricted knowledge of its substrate targets. Here we show capacity of human OCTN1-reconstituted proteoliposomes to mediate uptake and efflux of [(3)H]acetylcholine, the Km of transport being 1.0mM with V(max) of 160nmol⋅mg(-1)protein⋅min(-1). OCTN1-mediated transport of this neurotransmitter was time-dependent and was stimulated by intraliposomal ATP. The transporter operates as uniporter but translocates acetylcholine in both directions. [(3)H]acetylcholine uptake was competitively inhibited by tetraethylammonium, γ-butyrobetaine and acetylcarnitine, and was also inhibited by various polyamines. Decreasing intraliposomal ATP concentrations increased OCTN Km for acetylcholine, but V(max) was unaffected. Evaluation of the acetylcholine transporter properties of a variant form of OCTN1, the Crohn's disease-associated 503F variant, revealed time course, Km and V(max) for acetylcholine uptake to be comparable to that of wild-type OCTN1. Km for acetylcholine efflux was also comparable for both OCTN1 species, but V(max) of OCTN1 503F-mediated acetylcholine efflux (1.9nmol⋅mg(-1)protein⋅min(-1)) was significantly lower than that of wild-type OCTN1 (14nmol⋅mg(-1)protein⋅min(-1)). These data identify a new transport role for OCTN1 and raise the possibility that its involvement in the non-neuronal acetylcholine system may be relevant to the pathogenesis of Crohn's disease.
Lingua originaleEnglish
pagine (da-a)559-565
Numero di pagine7
RivistaBIOCHIMICA ET BIOPHYSICA ACTA
Volume1818
DOI
Stato di pubblicazionePubblicato - 2012

Keywords

  • Acetylcarnitine
  • Acetylcholine
  • Adenosine Triphosphate
  • Amino Acid Substitution
  • Betaine
  • Biological Transport, Active
  • Carnitine
  • Catalysis
  • Crohn Disease
  • Humans
  • Kinetics
  • Liposomes
  • Mutation, Missense
  • Nootropic Agents
  • Organic Cation Transport Proteins
  • Potassium Channel Blockers
  • Tetraethylammonium

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