title: PAX5 is the transcriptional activator of mucolipin-2 (MCOLN2) gene.
abstract: Transient receptor potential mucolipin (TRPML) proteins belong to the TRP superfamily of non-selective cation channels. The TRPML1, -2, and -3 proteins are encoded by Mucolipin (MCOLN)-1, -2 and -3 genes, respectively. TRPML1 has been associated with mucolipidosis type IV (MLIV), while no disease phenotype has been linked with TRPML2 or -3 protein. The TRPML proteins share high sequence similarities, form hetero-tetramers, and serve in membrane trafficking, autophagy, and metal homeostasis. Previous studies suggest that TRPML2 serves a role in the immune system; however, the evidence is mostly indirect. We hypothesize that if TRPML2 is involved in immune function its expression would be likely regulated by an immune-associated transcription factor protein. Thus, we set out to identify the core promoter region and the transcription factor responsible for MCOLN2 gene expression. Using dual-luciferase assay and over-expression analyses, we reveal for the first time that B-cell lineage specific activator protein (BSAP), also known as paired box 5 (PAX5), controls MCOLN2 expression. Specifically, heterologous expression of PAX5 in HEK-293 cells significantly increased endogenous MCOLN2 transcript and TRPML2 protein levels, while RNA interference targeting endogenous PAX5 reduced its effect. Site-directed mutagenesis studies showed that the core promoter and PAX5 binding region to be between -79 and -60 base pairs upstream of the transcriptional start site. Thus, our findings add to a growing list of evidence for TRPML2's possible involvement in the immune system. The knowledge gained from this study could be used to further characterize the role of TRPML2 in B-cell development and function.
authors.affiliation: Department of Biological Science, and Center for Applied Biotechnology Studies, California State University Fullerton, CA 92831, USA.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Valadez
authors.affiliation: Department of Biological Science, and Center for Applied Biotechnology Studies, California State University Fullerton, CA 92831, USA; Mental Health Research Institute, Melbourne Brain Centre, Parkville, Victoria 3052, Australia. Electronic address: mcuajungco@fullerton.edu.
authors.forename: Math P
authors.initials: MP
authors.lastname: Cuajungco
mesh_terms: D001402:B-Lymphocytes / Q000378:metabolism; D045744:Cell Line, Tumor; D002874:Chromosome Mapping; D018899:CpG Islands; D011992:Endosomes / Q000378:metabolism; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006706:Homeostasis; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D051757:PAX5 Transcription Factor / Q000378:metabolism*; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D034622:RNA Interference; D014157:Transcription Factors / Q000378:metabolism; D050051:Transient Receptor Potential Channels / Q000378:metabolism*
chemical_list: C510641:Mcoln2 protein, human; D051757:PAX5 Transcription Factor; C497281:PAX5 protein, human; D014157:Transcription Factors; D050051:Transient Receptor Potential Channels
keywords: B-cell; BSAP; Endosomes; Immune system; Lysosomes; Mucolipidosis IV; TRPML2