title: Regulatory Implications of Non-Trivial Splicing: Isoform 3 of Rab1A Shows Enhanced Basal Activity and Is Not Controlled by Accessory Proteins.
abstract: Alternative splicing often affects structured and highly conserved regions of proteins, generating so called non-trivial splicing variants of unknown structure and cellular function. The human small G-protein Rab1A is involved in the regulation of the vesicle transfer from the ER to Golgi. A conserved non-trivial splice variant lacks nearly 40% of the sequence of the native Rab1A, including most of the regulatory interaction sites. We show that this variant of Rab1A represents a stable and folded protein, which is still able to bind nucleotides and co-localizes with membranes. Nevertheless, it should be mentioned that compared to other wild-typeRabGTPases, the measured nucleotide binding affinities are dramatically reduced in the variant studied. Furthermore, the Rab1A variant forms hetero-dimers with wild-type Rab1A and its presence in the cell enhances the efficiency of alkaline phosphatase secretion. However, this variant shows no specificity for GXP nucleotides, a constantly enhanced GTP hydrolysis activity and is no longer controlled by GEF or GAP proteins, indicating a new regulatory mechanism for the Rab1A cycle via alternative non-trivial splicing.
authors.affiliation: Center for Integrated Protein Science, Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany.
authors.forename: Patricia
authors.initials: P
authors.lastname: Schöppner
authors.affiliation: Department of Informatics, Ludwig-Maximilians-Universität München, Amalienstr. 17, 80333 München, Germany.
authors.forename: Gergely
authors.initials: G
authors.lastname: Csaba
authors.affiliation: Center for Integrated Protein Science, Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Braun
authors.affiliation: Center for Integrated Protein Science, Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany.
authors.forename: Marina
authors.initials: M
authors.lastname: Daake
authors.affiliation: Center for Integrated Protein Science, Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Richter
authors.affiliation: Center for Integrated Protein Science, Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany.
authors.forename: Oliver F
authors.initials: OF
authors.lastname: Lange
authors.affiliation: Physics Department, Technische Universität München, James-Franck-Strasse 1, 85747 Garching, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Zacharias
authors.affiliation: Department of Informatics, Ludwig-Maximilians-Universität München, Amalienstr. 17, 80333 München, Germany. Electronic address: Ralf.Zimmer@ifi.lmu.de.
authors.forename: Ralf
authors.initials: R
authors.lastname: Zimmer
authors.affiliation: Center for Integrated Protein Science, Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany. Electronic address: martin.haslbeck@tum.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Haslbeck
mesh_terms: D017398:Alternative Splicing; D002462:Cell Membrane / Q000378:metabolism; D019143:Evolution, Molecular; D006153:Guanosine Diphosphate / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D009711:Nucleotides / Q000737:chemistry; D011485:Protein Binding; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D020543:Proteome; D020691:rab GTP-Binding Proteins / Q000737:chemistry; D020761:rab1 GTP-Binding Proteins / Q000737:chemistry*
chemical_list: D009711:Nucleotides; D020033:Protein Isoforms; D020543:Proteome; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D020691:rab GTP-Binding Proteins; D020761:rab1 GTP-Binding Proteins
keywords: Rab1A; non-trivial splicing; protein folding; protein secretion