SEL-2, the C. elegans neurobeachin/LRBA homolog, is a negative regulator of lin-12/Notch activity and affects endosomal traffic in polarized epithelial cells.
The vulval precursor cells (VPCs) of Caenorhabditis elegans are polarized epithelial cells that adopt a precise pattern of fates through regulated activity of basolateral LET-23/EGF receptor and apical LIN-12/Notch. During VPC patterning, there is reciprocal modulation of endocytosis and trafficking of both LET-23 and LIN-12. We identified sel-2 as a negative regulator of lin-12/Notch activity in the VPCs, and found that SEL-2 is the homolog of two closely related human proteins, neurobeachin (also known as BCL8B) and LPS-responsive, beige-like anchor protein (LRBA). SEL-2, neurobeachin and LRBA belong to a distinct subfamily of BEACH-WD40 domain-containing proteins. Loss of sel-2 activity leads to basolateral mislocalization and increased accumulation of LIN-12 in VPCs in which LET-23 is not active, and to impaired downregulation of basolateral LET-23 in VPCs in which LIN-12 is active. Downregulation of apical LIN-12 in the VPC in which LET-23 is active is not affected. In addition, in sel-2 mutants, the polarized cells of the intestinal epithelium display an aberrant accumulation of the lipophilic dye FM4-64 when the dye is presented to the basolateral surface. Our observations indicate that SEL-2/neurobeachin/LRBA is involved in endosomal traffic and may be involved in efficient delivery of cell surface proteins to the lysosome. Our results also suggest that sel-2 activity may contribute to the appropriate steady-state level of LIN-12 or to trafficking events that affect receptor activation.
de Souza
Natalie
N
Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, 701 W. 168th Street, Hammer Health Sciences, New York, NY 10032, USA.
Vallier
Laura G
LG
Fares
Hanna
H
Greenwald
Iva
I
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins; D016764:Cell Polarity; D017868:Cyclic AMP-Dependent Protein Kinases; D011992:Endosomes / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D009419:Nerve Tissue Proteins; D021381:Protein Transport; D051880:Receptors, Notch; D013234:Stem Cells; D014844:Vulva / Q000166:cytology
D048868:Adaptor Proteins, Signal Transducing; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; C082460:Lin-12 protein, C elegans; D008565:Membrane Proteins; C498595:NBEA protein, human; D009419:Nerve Tissue Proteins; D051880:Receptors, Notch; C519905:SEL-2 protein, C elegans; C428703:LRBA protein, human; D017868:Cyclic AMP-Dependent Protein Kinases