SEL-2, theC. elegansneurobeachin/LRBA homolog, is a negative regulator oflin-12/Notchactivity and affects endosomal traffic in polarized epithelial cells
Abstract: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 BC… Show more
“…12 LRBA is a member of a gene family involved in vesicle trafficking, 29,30 and we found that LRBA regulates CTLA-4 turnover in endosomes ( Figure 1C). 12 LRBA helps maintain an intracellular vesicular pool of CTLA-4 for immediate mobilization to the cell surface as needed.…”
Section: Blood 25 August 2016 X Volume 128 Number 8 Chai and Lataiementioning
CTLA-4 is a critical inhibitory âcheckpointâ molecule of immune activation. Several recent reports have described patients with immune dysregulation and lymphoproliferative disease resulting from 2 different genetic diseases that directly or indirectly cause CTLA-4 deficiency. Numerous articles have also been published describing CTLA-4 blockade in cancer immunotherapy and its side effects, which are ultimately the consequence of treatment-induced CTLA-4 deficiency. Here, we review these 2 diseases and CTLA-4 blockade therapy, emphasizing the crucial role of CTLA-4 in immune checkpoint regulation.
“…12 LRBA is a member of a gene family involved in vesicle trafficking, 29,30 and we found that LRBA regulates CTLA-4 turnover in endosomes ( Figure 1C). 12 LRBA helps maintain an intracellular vesicular pool of CTLA-4 for immediate mobilization to the cell surface as needed.…”
Section: Blood 25 August 2016 X Volume 128 Number 8 Chai and Lataiementioning
CTLA-4 is a critical inhibitory âcheckpointâ molecule of immune activation. Several recent reports have described patients with immune dysregulation and lymphoproliferative disease resulting from 2 different genetic diseases that directly or indirectly cause CTLA-4 deficiency. Numerous articles have also been published describing CTLA-4 blockade in cancer immunotherapy and its side effects, which are ultimately the consequence of treatment-induced CTLA-4 deficiency. Here, we review these 2 diseases and CTLA-4 blockade therapy, emphasizing the crucial role of CTLA-4 in immune checkpoint regulation.
“…Most commonly, endocytosis followed by receptor degradation terminates signaling. However, endocytosis can also prolong the duration of signaling (Jullien and Gurdon, 2005) or influence its subcellular location (de Souza et al, 2007;Howe and Mobley, 2005). Receptors may also signal through different downstream pathways localized to specialized endosomal compartments (Di Guglielmo et al, 2003;Miaczynska et al, 2004;Teis et al, 2006).…”
Section: Endocytosis and Receptor Signalingmentioning
Endocytosis of activated receptors can control signaling levels by exposing the receptors to novel downstream molecules or by instigating their degradation. Epidermal growth factor receptor (EGFR) signaling has crucial roles in development and is misregulated in many cancers. We report here that Myopic, the Drosophila homolog of the Bro1-domain tyrosine phosphatase HD-PTP, promotes EGFR signaling in vivo and in cultured cells. myopic is not required in the presence of activated Ras or in the absence of the ubiquitin ligase Cbl, indicating that it acts on internalized EGFR, and its overexpression enhances the activity of an activated form of EGFR. Myopic is localized to intracellular vesicles adjacent to Rab5-containing early endosomes, and its absence results in the enlargement of endosomal compartments. Loss of Myopic prevents cleavage of the EGFR cytoplasmic domain, a process controlled by the endocytic regulators Cbl and Sprouty. We suggest that Myopic promotes EGFR signaling by mediating its progression through the endocytic pathway.
KEY WORDS: ESCRT complex, MAP kinase, HD-PTP (PTPN23), Bro1 domain, Photoreceptor
“…Bchs is a member of the Beige and Chediak-Higashi (BEACH) family of proteins whose role in vesicular trafficking has been described previously (Wang et al, 2000;Ward et al, 2000;Cornillon et al, 2002;Su et al, 2004;de Souza et al, 2007). The abnormal accumulation of ubiquitinated proteins in bchs brain tissue and the ability of lysosomal mutations to suppress a Bchs overexpression eye phenotype, suggested a possible role in degradation (Finley et al, 2003).…”
., 2007). Here, we describe the degeneration of a population of identified larval motor neurons in bchs mutants. We present evidence that Bchs is primarily lysosomal in those motor neurons in wild type and, using live fluorescence imaging of individual motor neurons in intact larvae, show that lysosomal vesicles fail to be transported toward motor neuron termini in bchs mutant and Bchs-overexpressing larvae. We suggest therefore that anterograde transport of lysosomes toward synaptic termini is a key factor in preventing motor neuron degeneration and that Bchs reveals a functional link between the lysosomal degradative pathway and transport.
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