J Cell Sci. 2011 Feb 1;124(Pt 3):459-68. doi: 10.1242/jcs.076240. Epub 2011 Jan 11.
LAPTMs regulate lysosomal function and interact with mucolipin 1: new clues for understanding mucolipidosis type IV.
Vergarajauregui, S., Martina, J. A., Puertollano, R.,
["Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA."]
["Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA."]
Loss-of-function mutations in mucolipin 1 (MCOLN1) result in mucolipidosis type IV (MLIV), a lysosomal storage disorder characterized by severe mental and psychomotor retardation. MCOLN1 is a lysosomal ion channel that belongs to the transient receptor potential (TRP) superfamily. To better understand the cellular function of MCOLN1, a split-ubiquitin yeast two-hybrid screen was performed with the purpose of revealing new MCOLN1 interaction partners. The screen identified two members of the lysosome-associated protein transmembrane (LAPTM) family as novel interaction partners of MCOLN1. The binding between MCOLN1 and LAPTM members (LAPTMs) was confirmed by co-immunoprecipitation and yeast two-hybrid assays. In addition, MCOLN1 and LAPTMs extensively colocalize at late endosomes and lysosomes. Overexpression of LAPTM4b caused enlargement of lysosomes and defective lysosomal degradation, indicating that LAPTMs are important for proper lysosomal function. Interestingly, lysosomal swelling induced by LAPTM4b was rescued by expression of MCOLN1, suggesting a functional connection between the two proteins. Finally, depletion of endogenous LAPTMs by siRNA induced accumulation of concentric multi-lamellar structures and electron-dense inclusions that closely resemble the structures found in MLIV cells. Overall, our data provide new insight into the molecular mechanisms of MCOLN1 function and suggest a potential role for LAPTMs in MLIV pathogenesis.
PMID: 21224396

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Screening
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Experimental screening | Non-experimental screening | Reference | ||||||||
TRP channel construct | Interactor source | |||||||||
TRP channel | Interactor | Method | Species | Region | Species | Organ/tissue | Sample type | |||
TRPML1 |
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LAPTM4a | Yeast two-hybrid | Human | Full-length | Human | adult brain | cDNA library | 21224396 | |
TRPML1 |
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LAPTM4b | Yeast two-hybrid | Human | Full-length | Human | adult brain | cDNA library | 21224396 | |
TRPML1 |
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LAPTM5 | Speculation | Prediction | 21224396 |
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)

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Validation: In vitro validation
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Assay with recombinant proteins | Reference | |||||||||
TRP channel construct | Interactor construct | |||||||||
TRP channel | Interactor | Method | Species | Region | Expression system | Species | Region | Expression system | ||
TRPML1 |
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LAPTM4a | Yeast two-hybrid | Human | Full-length | Yeast | Human | 1-651 | Yeast | 21224396 |
TRPML1 |
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LAPTM4b | Yeast two-hybrid | Human | Full-length | Yeast | Human | 79-141 | Yeast | 21224396 |
TRPML1 |
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LAPTM5 | Yeast two-hybrid | Human | Full-length | Yeast | Human | Not specified | Yeast | 21224396 |
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)

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Validation: In vivo validation
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Assay with endogenous proteins | Assay with overexpressed proteins | Reference | ||||||||
Cell or tissue | Cell or tissue | TRP channel construct | Interactor construct | |||||||
TRP channel | Interactor | Method | Species | Region | Species | Region | ||||
TRPML1 |
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LAPTM4a | Co-immunoprecipitation | HeLa | Human | Full-length | Human | Full-length | 21224396 | |
TRPML1 |
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LAPTM4a | Co-immunofluorescence staining | ARPE-19 | Human | Full-length | Human | Full-length | 21224396 | |
TRPML1 |
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LAPTM4b | Co-immunoprecipitation | HeLa | Human | Full-length | Human | Full-length | 21224396 | |
TRPML1 |
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LAPTM4b | Co-immunofluorescence staining | ARPE-19 | Human | Full-length | Human | Full-length | 21224396 | |
TRPML1 |
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LAPTM5 | Co-immunoprecipitation | HeLa | Human | Full-length | Human | Full-length | 21224396 | |
TRPML1 |
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LAPTM5 | Co-immunofluorescence staining | ARPE-19 | Human | Full-length | Human | Full-length | 21224396 |
(
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
