title: RIN3 is a negative regulator of mast cell responses to SCF.
abstract: Stimulation of the receptor tyrosine kinase KIT by Stem Cell Factor (SCF) triggers activation of RAS and its downstream effectors. Proper KIT activation is essential for the maturation, survival and proliferation of mast cells. In addition, SCF activation of KIT is critical for recruiting mast cells to sites of infection or injury, where they release a mix of pro-inflammatory substances. RIN3, a RAS effector and RAB5-directed guanine nucleotide exchange factor (GEF), is highly expressed and enriched in human mast cells. SCF treatment of mast cells increased the amount of GTP-bound RAB5, and the degree of RAB5 activation correlated with the expression level of RIN3. At the same time, SCF caused the dissociation of a pre-formed complex of RIN3 with BIN2, a membrane bending protein implicated in endocytosis. Silencing of RIN3 increased the rate of SCF-induced KIT internalization, while persistent RIN3 over-expression led to KIT down regulation. These observations strongly support a role for RIN3 in coordinating the early steps of KIT endocytosis. Importantly, RIN3 also functioned as an inhibitor of mast cell migration toward SCF. Finally, we demonstrate that elevated RIN3 levels sensitize mastocytosis cells to treatment with a KIT tyrosine kinase inhibitor, suggesting the value of a two-pronged inhibitor approach for this difficult to treat malignancy. These findings directly connect KIT activation with a mast cell-specific RAS effector that regulates the cellular response to SCF and provide new insight for the development of more effective mastocytosis treatments.
authors.affiliation: Molecular Biology Institute, Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Christine
authors.initials: C
authors.lastname: Janson
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kasahara
authors.forename: George C
authors.initials: GC
authors.lastname: Prendergast
authors.forename: John
authors.initials: J
authors.lastname: Colicelli
mesh_terms: D001549:Benzamides / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D002465:Cell Movement; D049109:Cell Proliferation; D004705:Endocytosis; D005786:Gene Expression Regulation; D020868:Gene Silencing; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D007150:Immunohistochemistry / Q000379:methods; D007249:Inflammation; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis; D008407:Mast Cells / Q000166:cytology*; D008415:Mastocytosis / Q000473:pathology; D010879:Piperazines / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D019089:Stem Cell Factor / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D001549:Benzamides; D002352:Carrier Proteins; D020662:Guanine Nucleotide Exchange Factors; D018950:Lipopolysaccharide Receptors; D010879:Piperazines; D011743:Pyrimidines; C487967:RIN3 protein, human; D019089:Stem Cell Factor; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit; D020696:rab5 GTP-Binding Proteins