title: The Ca(2+) channel TRPML3 regulates membrane trafficking and autophagy.
abstract: TRPML3 is an inward rectifying Ca(2+) channel that is regulated by extracytosolic H(+). Although gain-of-function mutation in TRPML3 causes the varitint-waddler phenotype, the role of TRPML3 in cellular physiology is not known. In this study, we report that TRPML3 is a prominent regulator of endocytosis, membrane trafficking and autophagy. Gradient fractionation and confocal localization reveal that TRPML3 is expressed in the plasma membrane and multiple intracellular compartments. However, expression of TRPML3 is dynamic, with accumulation of TRPML3 in the plasma membrane upon inhibition of endocytosis, and recruitment of TRPML3 to autophagosomes upon induction of autophagy. Accordingly, overexpression of TRPML3 leads to reduced constitutive and regulated endocytosis, increased autophagy and marked exacerbation of autophagy evoked by various cell stressors with nearly complete recruitment of TRPML3 into the autophagosomes. Importantly, both knockdown of TRPML3 by siRNA and expression of the channel-dead dominant negative TRPML3(D458K) have a reciprocal effect, reducing endocytosis and autophagy. These findings reveal a prominent role for TRPML3 in regulating endocytosis, membrane trafficking and autophagy, perhaps by controlling the Ca(2+) in the vicinity of cellular organelles that is necessary to regulate these cellular events.
authors.affiliation: Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Abigail A
authors.initials: AA
authors.lastname: Soyombo
authors.forename: Sandra
authors.initials: S
authors.lastname: Tjon-Kon-Sang
authors.forename: Insuk
authors.initials: I
authors.lastname: So
authors.forename: Shmuel
authors.initials: S
authors.lastname: Muallem
mesh_terms: D000818:Animals; D001343:Autophagy / Q000502:physiology*; D001692:Biological Transport / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004705:Endocytosis / Q000502:physiology; D004815:Epidermal Growth Factor / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006801:Humans; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D018408:Patch-Clamp Techniques; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D050053:TRPM Cation Channels / Q000235:genetics / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism; D050051:Transient Receptor Potential Channels / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D002118:Calcium; D004815:Epidermal Growth Factor; D051907:Lysosomal Membrane Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D050053:TRPM Cation Channels; D014168:Transferrin; D050051:Transient Receptor Potential Channels; D033921:Vesicular Transport Proteins; C489116:LAMP1 protein, human; D052118:Lysosomal-Associated Membrane Protein 1; C416674:MCOLN1 protein, human; C510642:MCOLN3 protein, human; C093846:early endosome antigen 1