TRP-ML1 is a lysosomal monovalent cation channel that undergoes proteolytic cleavage.
Mutations in the gene MCOLN1 coding for the TRP (transient receptor potential) family ion channel TRP-ML1 lead to the lipid storage disorder mucolipidosis type IV (MLIV). The function and role of TRP-ML1 are not well understood. We report here that TRP-ML1 is a lysosomal monovalent cation channel. Both native and recombinant TRP-ML1 are cleaved resulting in two products. Recombinant TRP-ML1 is detected as the full-length form and as short N- and C-terminal forms, whereas in native cells mainly the cleaved N and C termini are detected. The N- and C-terminal fragments of TRP-ML1 were co-immunoprecipitated from cell lysates and co-eluted from a Ni2+ column. TRP-ML1 undergoes proteolytic cleavage that is inhibited by inhibitors of cathepsin B (CatB) and is altered when TRP-ML1 is expressed in CatB-/- cells. N-terminal sequencing of purified C-terminal fragment of TRP-ML1 expressed in Sf9 cells indicates a cleavage site at Arg200 downward arrow Pro201. Consequently, the conserved R200H mutation changed the cleavage pattern of TRP-ML1. The cleavage inhibited TRP-ML1 channel activity. This work provides the first example of inactivation by cleavage of a TRP channel. The significance of the cleavage to the function of TRP-ML1 is under investigation.
Kiselyov
Kirill
K
Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
Chen
Jin
J
Rbaibi
Youssef
Y
Oberdick
Daniel
D
Tjon-Kon-Sang
Sandra
S
Shcheynikov
Nikolay
N
Muallem
Shmuel
S
Soyombo
Abigail
A
D000818:Animals; D001120:Arginine / Q000737:chemistry; D001665:Binding Sites; D002412:Cations; D002460:Cell Line; D004594:Electrophysiology; D005347:Fibroblasts / Q000166:cytology; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D007313:Insecta; D008055:Lipids / Q000737:chemistry; D008247:Lysosomes / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D008856:Microscopy, Fluorescence; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009532:Nickel / Q000737:chemistry; D011392:Proline / Q000737:chemistry; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D012867:Skin / Q000166:cytology; D050053:TRPM Cation Channels; D050051:Transient Receptor Potential Channels / Q000378:metabolism / Q000502:physiology*
D002412:Cations; D008055:Lipids; C416674:MCOLN1 protein, human; D008565:Membrane Proteins; D011994:Recombinant Proteins; D050053:TRPM Cation Channels; D050051:Transient Receptor Potential Channels; D009532:Nickel; D001120:Arginine; D011392:Proline