IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Molecular dissection of Glucosidase II, a key element in preventing glycoprotein misfolding
Autor/es:
IVÁN STIGLIANO; CARLOS LABRIOLA; JULIO CARAMELO; CECILIA D'ALESSIO; ARMANDO J. PARODI
Lugar:
Tel Aviv-Israel
Reunión:
Simposio; Protein misfolding in the test tube and disease; 2009
Institución organizadora:
University of Tel Aviv
Resumen:
<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman"; mso-bidi-language:AR-SA;} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Molecular dissection of Glucosidase II, a key element in preventing glycoprotein misfolding Stigliano I, Labriola C, Caramelo J, D’Alessio C and Parodi A.   Glucosidase II (GII) is a key player in glycoprotein biogenesis in the endoplasmic reticulum (ER) as it is responsible fot the sequential removal of the two innermost glucose residues from the glycan (Glc3Man9GlcNac2) transferred to Asn residues in proteins (N-glycosylation). Furthermore, GII participates in the so called calnexin/calreticulin cycle as it removes the single glucose unit added to folding intermediates and misfolded glycoproteins by the UDP-Glc:glycoprotein glucosyltransferase. GII is a heterodimer whose alfa subunit (GIIalfa) bears the glycosyl hydrolase active site. The B subunit (GIIbeta) has been reported to be involved in GIIalfa ER retention, maturation, glycan recognition as well as in cell development and human disease. Here we report that in the absence of GIIbeta the catalytic subunit of the fission yeast Schizosaccharomyces pombe (an organism displaying a glycoprotein folding quality control mechanism similar to that ocurring in mammalian cells) matures to an active conformation able to hydrolyze the sustrate analogue p-nitrophenyl glucoside (pNPG) but very poorly the physiological substrates Glc2Man9GlcNac (G2M9) and Glc1Man9GlcNac (G1M9) and is sub optimally reatained in the ER. However the heterodimer is required to efficiently deglucosylate both G2M9 and G1M9. The interaction of the mannose 6-phospate receptor domain present in GIIbeta and mannoses in the B and/or C arms of the glycans mediates glycan hydrolysis enhancement. In addition, the VDEL sequence present at the GIIbeta C-terminus is required for optimal Er GII localization. Evidence is presented that also in mammalian cells GIIbeta modulates G2M9 and G1M9 deglucosylation