The tissue-specific expression of TRPML2 (MCOLN-2) gene is influenced by the presence of TRPML1.
Mucolipidosis type IV is a lysosomal storage disorder caused by the loss or dysfunction of the mucolipin-1 (TRPML1) protein. It has been suggested that TRPML2 could genetically compensate (i.e., become upregulated) for the loss of TRPML1. We thus investigated this possibility by first studying the expression pattern of mouse TRPML2 and its basic channel properties using the varitint-waddler (Va) model. Here, we confirmed the presence of long variant TRPML2 (TRPML2lv) and short variant (TRPML2sv) isoforms. We showed for the first time that, heterologously expressed, TRPML2lv-Va is an active, inwardly rectifying channel. Secondly, we quantitatively measured TRPML2 and TRPML3 mRNA expressions in TRPML1-/- null and wild-type (Wt) mice. In wild-type mice, the TRPML2lv transcripts were very low while TRPML2sv and TRPML3 transcripts have predominant expressions in lymphoid and kidney organs. Significant reductions of TRPML2sv, but not TRPML2lv or TRPML3 transcripts, were observed in lymphoid and kidney organs of TRPML1-/- mice. RNA interference of endogenous human TRPML1 in HEK-293 cells produced a comparable decrease of human TRPML2 transcript levels that can be restored by overexpression of human TRPML1. Conversely, significant upregulation of TRPML2sv transcripts was observed when primary mouse lymphoid cells were treated with nicotinic acid adenine dinucleotide phosphate, or N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinoline sulfonamide, both known activators of TRPML1. In conclusion, our results indicate that TRPML2 is unlikely to compensate for the loss of TRPML1 in lymphoid or kidney organs and that TRPML1 appears to play a novel role in the tissue-specific transcriptional regulation of TRPML2.
Samie
Mohammad A
MA
Department of Biological Science, and Center for Applied, Biotechnology Studies, California State University Fullerton, 800 N State College Blvd, Fullerton, CA 92831, USA.
Grimm
Christian
C
Evans
Jeffrey A
JA
Curcio-Morelli
Cyntia
C
Heller
Stefan
S
Slaugenhaupt
Susan A
SA
Cuajungco
Math P
MP
D000818:Animals; D002460:Cell Line; D004195:Disease Models, Animal; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009081:Mucolipidoses / Q000235:genetics* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050053:TRPM Cation Channels / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D050051:Transient Receptor Potential Channels / Q000235:genetics / Q000378:metabolism
C510642:MCOLN3 protein, human; C512321:Mcoln1 protein, mouse; C505823:Mcoln2 protein, mouse; D020033:Protein Isoforms; D050053:TRPM Cation Channels; D050051:Transient Receptor Potential Channels