Stability of proICA512/IA-2 and its targeting to insulin secretory granules require β4-sheet-mediated dimerization of its ectodomain in the endoplasmic reticulum
| Autor: | Juha M. Torkko, Antje Viehrig, Michele Solimena, Barbara Borgonovo, Martina Lachnit, Carolin Wegbrod, Ronald Dirkx, Carla Münster, Anke Sönmez, Mario R. Ermácora, Mauricio P. Sica, María E. Primo, Anne Friedrich, Elisa Vergari |
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| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: |
endocrine system
Glycosylation Otras Ciencias Biológicas Biología Mutant Molecular Sequence Data Protein tyrosine phosphatase Biology Cytoplasmic Granules Endoplasmic Reticulum SECRESION GRANULES Ciencias Biológicas purl.org/becyt/ford/1 [https] chemistry.chemical_compound Islets of Langerhans Cytosol Animals Insulin Receptor-Like Protein Tyrosine Phosphatases Class 8 DIABETES Amino Acid Sequence Protein tyrosine kinase purl.org/becyt/ford/1.6 [https] Molecular Biology Cells Cultured Endoplasmic reticulum Secretory Vesicles Granule (cell biology) STIM1 Cell Biology Articles INSULIN Cell biology Protein Structure Tertiary Rats ICA512 chemistry Ectodomain Microsome Dimerization CIENCIAS NATURALES Y EXACTAS |
| Zdroj: | CONICET Digital (CONICET) Consejo Nacional de Investigaciones Científicas y Técnicas instacron:CONICET SEDICI (UNLP) Universidad Nacional de La Plata instacron:UNLP |
| Popis: | The type 1 diabetes autoantigen ICA512/IA-2/RPTPN is a receptor protein tyrosine phosphatase of the insulin secretory granules (SGs) which regulates the size of granule stores, possibly via cleavage/signaling of its cytosolic tail. The role of its extracellular region remains unknown. Structural studies indicated that β2- or β4-strands in the mature ectodomain (ME ICA512) form dimers in vitro. Here we show that ME ICA512 prompts proICA512 dimerization in the endoplasmic reticulum. Perturbation of ME ICA512 β2-strand N-glycosylation upon S508A replacement allows for proICA512 dimerization, O-glycosylation, targeting to granules, and conversion, which are instead precluded upon G553D replacement in the ME ICA512 β4-strand. S508A/G553D and N506A/G553D double mutants dimerize but remain in the endoplasmic reticulum. Removal of the N-terminal fragment (ICA512-NTF) preceding ME ICA512 allows an ICA512-ΔNTF G553D mutant to exit the endoplasmic reticulum, and ICA512-ΔNTF is constitutively delivered to the cell surface. The signal for SG sorting is located within the NTF RESP18 homology domain (RESP18-HD), whereas soluble NTF is retained in the endoplasmic reticulum. Hence, we propose that the ME ICA512 β2-strand fosters proICA512 dimerization until NTF prevents N506 glycosylation. Removal of this constraint allows for proICA512 β4-strand-induced dimerization, exit from the endoplasmic reticulum, O-glycosylation, and RESP18-HD-mediated targeting to granules. Instituto Multidisciplinario de Biología Celular |
| Databáze: | OpenAIRE |
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