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The Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for dendrite formation in melanocytes
Vacuolar protein sorting 9 (VPS9)–ankyrin-repeat protein (Varp) has recently been identified as an effector molecule for two small GTPases—Rab32 and Rab38—in the transport of a melanogenic enzyme tyrosinase-related protein 1 (Tyrp1) to melanosomes in melanocytes. Although Varp contains a Rab21–guani...
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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The American Society for Cell Biology
2012
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3279394/ https://www.ncbi.nlm.nih.gov/pubmed/22171327 http://dx.doi.org/10.1091/mbc.E11-04-0324 |
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author | Ohbayashi, Norihiko Yatsu, Ayaka Tamura, Kanako Fukuda, Mitsunori |
author_facet | Ohbayashi, Norihiko Yatsu, Ayaka Tamura, Kanako Fukuda, Mitsunori |
author_sort | Ohbayashi, Norihiko |
collection | PubMed |
description | Vacuolar protein sorting 9 (VPS9)–ankyrin-repeat protein (Varp) has recently been identified as an effector molecule for two small GTPases—Rab32 and Rab38—in the transport of a melanogenic enzyme tyrosinase-related protein 1 (Tyrp1) to melanosomes in melanocytes. Although Varp contains a Rab21–guanine nucleotide exchange factor (GEF) domain (i.e., VPS9 domain), since Rab21-GEF activity is not required for Tyrp1 transport, nothing is known about the physiological significance of the Rab21-GEF activity in melanocytes. Here we show by knockdown-rescue experiments that the Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for forskolin-induced dendrite formation of cultured melanocytes. We found that Varp-deficient cells are unable to extend dendrites in response to forskolin stimulation and that reexpression of wild-type Varp or a Rab32/38-binding–deficient mutant Varp(Q509A/Y550A) in Varp-deficient cells completely restores their ability to form dendrites. By contrast, VPS9 mutants (D310A and Y350A) and a vesicle-associated membrane protein 7 (VAMP7)-binding–deficient mutant were unable to support forskolin-induced dendrite formation in Varp-deficient cells. These findings indicate that the Rab21-GEF activity and Rab32/38 binding activity of Varp are required for different melanocyte functions, that is, Rab21 activation by the VPS9 domain is required for dendrite formation, and the Rab32/38 effector function of the ankyrin repeat 1 domain is required for Tyrp1 transport to melanosomes, although VAMP7-binding ability is required for both functions. |
format | Online Article Text |
id | pubmed-3279394 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2012 |
publisher | The American Society for Cell Biology |
record_format | MEDLINE/PubMed |
spelling | pubmed-32793942012-04-30 The Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for dendrite formation in melanocytes Ohbayashi, Norihiko Yatsu, Ayaka Tamura, Kanako Fukuda, Mitsunori Mol Biol Cell Articles Vacuolar protein sorting 9 (VPS9)–ankyrin-repeat protein (Varp) has recently been identified as an effector molecule for two small GTPases—Rab32 and Rab38—in the transport of a melanogenic enzyme tyrosinase-related protein 1 (Tyrp1) to melanosomes in melanocytes. Although Varp contains a Rab21–guanine nucleotide exchange factor (GEF) domain (i.e., VPS9 domain), since Rab21-GEF activity is not required for Tyrp1 transport, nothing is known about the physiological significance of the Rab21-GEF activity in melanocytes. Here we show by knockdown-rescue experiments that the Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for forskolin-induced dendrite formation of cultured melanocytes. We found that Varp-deficient cells are unable to extend dendrites in response to forskolin stimulation and that reexpression of wild-type Varp or a Rab32/38-binding–deficient mutant Varp(Q509A/Y550A) in Varp-deficient cells completely restores their ability to form dendrites. By contrast, VPS9 mutants (D310A and Y350A) and a vesicle-associated membrane protein 7 (VAMP7)-binding–deficient mutant were unable to support forskolin-induced dendrite formation in Varp-deficient cells. These findings indicate that the Rab21-GEF activity and Rab32/38 binding activity of Varp are required for different melanocyte functions, that is, Rab21 activation by the VPS9 domain is required for dendrite formation, and the Rab32/38 effector function of the ankyrin repeat 1 domain is required for Tyrp1 transport to melanosomes, although VAMP7-binding ability is required for both functions. The American Society for Cell Biology 2012-02-15 /pmc/articles/PMC3279394/ /pubmed/22171327 http://dx.doi.org/10.1091/mbc.E11-04-0324 Text en © 2012 Ohbayashi et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0). “ASCB®,” “The American Society for Cell Biology®,” and “Molecular Biology of the Cell®” are registered trademarks of The American Society of Cell Biology. |
spellingShingle | Articles Ohbayashi, Norihiko Yatsu, Ayaka Tamura, Kanako Fukuda, Mitsunori The Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for dendrite formation in melanocytes |
title | The Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for dendrite formation in melanocytes |
title_full | The Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for dendrite formation in melanocytes |
title_fullStr | The Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for dendrite formation in melanocytes |
title_full_unstemmed | The Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for dendrite formation in melanocytes |
title_short | The Rab21-GEF activity of Varp, but not its Rab32/38 effector function, is required for dendrite formation in melanocytes |
title_sort | rab21-gef activity of varp, but not its rab32/38 effector function, is required for dendrite formation in melanocytes |
topic | Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3279394/ https://www.ncbi.nlm.nih.gov/pubmed/22171327 http://dx.doi.org/10.1091/mbc.E11-04-0324 |
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