title: Presynaptic BK channel localization is dependent on the hierarchical organization of alpha-catulin and dystrobrevin and fine-tuned by CaV2 calcium channels.
abstract: BACKGROUND
  Large conductance, calcium-activated BK channels regulate many important physiological processes, including smooth muscle excitation, hormone release and synaptic transmission. The biological roles of these channels hinge on their unique ability to respond synergistically to both voltage and cytosolic calcium elevations. Because calcium influx is meticulously regulated both spatially and temporally, the localization of BK channels near calcium channels is critical for their proper function. However, the mechanism underlying BK channel localization near calcium channels is not fully understood.
  
  
  RESULTS
  We show here that in C. elegans the localization of SLO-1/BK channels to presynaptic terminals, where UNC-2/CaV2 calcium channels regulate neurotransmitter release, is controlled by the hierarchical organization of CTN-1/α-catulin and DYB-1/dystrobrevin, two proteins that interact with cortical cytoskeletal proteins. CTN-1 organizes a macromolecular SLO-1 channel complex at presynaptic terminals by direct physical interaction. DYB-1 contributes to the maintenance or stabilization of the complex at presynaptic terminals by interacting with CTN-1. We also show that SLO-1 channels are functionally coupled with UNC-2 calcium channels, and that normal localization of SLO-1 to presynaptic terminals requires UNC-2. In the absence of UNC-2, SLO-1 clusters lose the localization specificity, thus accumulating inside and outside of presynaptic terminals. Moreover, CTN-1 is also similarly localized in unc-2 mutants, consistent with the direct interaction between CTN-1 and SLO-1. However, localization of UNC-2 at the presynaptic terminals is not dependent on either CTN-1 or SLO-1. Taken together, our data strongly suggest that the absence of UNC-2 indirectly influences SLO-1 localization via the reorganization of cytoskeletal proteins.
  
  
  CONCLUSIONS
  CTN-1 and DYB-1, which interact with cortical cytoskeletal proteins, are required for the presynaptic punctate localization of SLO-1 in a hierarchical manner. In addition, UNC-2 calcium channels indirectly control the fidelity of SLO-1 puncta localization at presynaptic terminals. We suggest that the absence of UNC-2 leads to the reorganization of the cytoskeletal structure that includes CTN-1, which in turn influences SLO-1 puncta localization.
authors.affiliation: Department of Cell Biology & Anatomy, Chicago Medical School, Rosalind Franklin University, 60064, North Chicago, IL, USA. kelly.oh@rosalindfranklin.edu.
authors.forename: Kelly H
authors.initials: KH
authors.lastname: Oh
authors.affiliation: Department of Cell Biology & Anatomy, Chicago Medical School, Rosalind Franklin University, 60064, North Chicago, IL, USA. linusara@gmail.com.
authors.forename: Linu S
authors.initials: LS
authors.lastname: Abraham
authors.affiliation: College of Computing and Digital Media, DePaul University, 60604, Chicago, IL, USA. chandlergegg@gmail.com.
authors.forename: Chandler
authors.initials: C
authors.lastname: Gegg
authors.affiliation: Department of Cell Biology & Anatomy, Chicago Medical School, Rosalind Franklin University, 60064, North Chicago, IL, USA. silvestricf@mx.lakeforest.edu.|Department of Biology, Lake Forest College, 60045, Lake Forest, IL, USA. silvestricf@mx.lakeforest.edu.
authors.forename: Christian
authors.initials: C
authors.lastname: Silvestri
authors.affiliation: Department of Neurobiology, University of Massachusetts Medical School, 01605, Worcester, MA, USA. Yung-Chi.Huang@umassmed.edu.
authors.forename: Yung-Chi
authors.initials: YC
authors.lastname: Huang
authors.affiliation: Department of Neurobiology, University of Massachusetts Medical School, 01605, Worcester, MA, USA. Mark.Alkema@umassmed.edu.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Alkema
authors.affiliation: College of Computing and Digital Media, DePaul University, 60604, Chicago, IL, USA. jfurst@cdm.depaul.edu.
authors.forename: Jacob
authors.initials: J
authors.lastname: Furst
authors.affiliation: College of Computing and Digital Media, DePaul University, 60604, Chicago, IL, USA. draicu@cdm.depaul.edu.
authors.forename: Daniela
authors.initials: D
authors.lastname: Raicu
authors.affiliation: Department of Cell Biology & Anatomy, Chicago Medical School, Rosalind Franklin University, 60064, North Chicago, IL, USA. hongkyun.kim@rosalindfranklin.edu.
authors.forename: Hongkyun
authors.initials: H
authors.lastname: Kim
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D008124:Locomotion / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism*; D051178:alpha Catenin / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; C479075:Dyb-1 protein, C elegans; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D051178:alpha Catenin; C494845:slo-1 protein, C elegans; C093204:unc-2 protein, C elegans