title: Regulation of RasGRP1 by B cell antigen receptor requires cooperativity between three domains controlling translocation to the plasma membrane.
abstract: RasGRP1 is a Ras-activating exchange factor that is positively regulated by translocation to membranes. RasGRP1 contains a diacylglycerol-binding C1 domain, and it has been assumed that this domain is entirely responsible for RasGRP1 translocation. We found that the C1 domain can contribute to plasma membrane-targeted translocation of RasGRP1 induced by ligation of the B cell antigen receptor (BCR). However, this reflects cooperativity of the C1 domain with the previously unrecognized Plasma membrane Targeter (PT) domain, which is sufficient and essential for plasma membrane targeting of RasGRP1. The adjacent suppressor of PT (SuPT) domain attenuates the plasma membrane-targeting activity of the PT domain, thus preventing constitutive plasma membrane localization of RasGRP1. By binding to diacylglycerol generated by BCR-coupled phospholipase Cgamma2, the C1 domain counteracts the SuPT domain and enables efficient RasGRP1 translocation to the plasma membrane. In fibroblasts, the PT domain is inactive as a plasma membrane targeter, and the C1 domain specifies constitutive targeting of RasGRP1 to internal membranes where it can be activated and trigger oncogenic transformation. Selective use of the C1, PT, and SuPT domains may contribute to the differential targeting of RasGRP1 to the plasma membrane versus internal membranes, which has been observed in lymphocytes and other cell types.
authors.affiliation: Terry Fox Laboratory, British Columbia Cancer Research Centre, Vancouver, BC, Canada V5Z 1L3.
authors.forename: Nadine
authors.initials: N
authors.lastname: Beaulieu
authors.forename: Bari
authors.initials: B
authors.lastname: Zahedi
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Goulding
authors.forename: Ghazaleh
authors.initials: G
authors.lastname: Tazmini
authors.forename: Kira V
authors.initials: KV
authors.lastname: Anthony
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Omeis
authors.forename: Danielle R
authors.initials: DR
authors.lastname: de Jong
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Kay
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D002645:Chickens; D005347:Fibroblasts / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D051966:Phospholipase C gamma / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D020662:Guanine Nucleotide Exchange Factors; C112278:Rasgrp1 protein, mouse; D011947:Receptors, Antigen, B-Cell; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D051966:Phospholipase C gamma