Biology subjects

Winistorfer, S.

Publications and source records attributed to Winistorfer, S..

4 recordsLinked to original sources

bioRxiv2025

K48-ubiquitin-activated proteases cut-up post-ER proteins

Polyubiquitin chains, linked via K48 or K63 of ubiquitin, target membrane proteins in the secretory system to degradative pathways. However its unclear whether these linkage isomers are functionally interchangeable. Here we show that for post-endoplasmic reticulum (ER) proteins, K63-linked polyubiquitination induces multivesicular bodies (MVBs) sorting and lysosomal degradation. In contrast, K48-linked polyubiquitination induces shearing from the membrane. Substrates are cleaved by the proteasome and by two ubiquitin-activated proteases: Ddi1, a conserved cytosolic ubiquilin that generates cytosolic fragments, and Rbd2, an intramembrane rhomboid protease that produces lumenal fragments. Rbd2 localizes to Golgi/endosomes but also acts on ubiquitinated substrates at the vacuolar membrane. Ddi1s catalytic core, the HDD-RVP domain is sufficient for ubiquitin-dependent proteolysis. It binds ubiquitin directly and its activity is amplified by auxiliary ubiquitin binding domains: an atypical UBL domain and a UBA domain. These findings demonstrate that polyubiquitin chains linked by different residues encode distinct degradative fates for post-ER proteins, and reveals two proteases that target ubiquitinated integral membrane cargo.

cell biology↗

bioRxiv2024

Insulated piggyBac and FRT vectors for engineering transgenic homozygous and heterozygous eHAP cells

Transgene expression in eHAP cells, a haploid cell line popularly used to generate gene knockouts, is difficult owing to its low transfection efficiency and propensity for silencing integrated transgenes. To simplify transgene expression, we engineered insulated integrating plasmids that sustain high levels of transgene expression in eHAP cells, and that can be used in other cell lines. These vectors are compatible with FLP-FRT and piggyBac integration, they flank a gene-of interest bilaterally with tandem cHS4 core insulators, and co-express nuclear-localized blue fluorescent protein for identification of high expressing cells. We further demonstrate that transgenic haploid eHAP cells can be fused to form transgenic heterozygous diploid cells. This method creates diploid cells carrying the transgenic material of the haploid progenitors and could also be used to create heterozygous cells of defined genotypes. These tools expand the repertoire of experiments that can be performed in eHAP cells and other cultured cells.

cell biology↗

bioRxiv2023

PMP22 associates with MPZ via their transmembrane domains and disrupting this interaction causes a loss-of-function phenotype similar to hereditary neuropathy associated with liability to pressure palsies (HNPP).

PMP22 and MPZ are abundant myelin membrane proteins in Schwann cells. The MPZ adhesion protein holds myelin wraps together across the intraperiod line. PMP22 is a tetraspan protein belonging to the Claudin superfamily. Loss of either MPZ or PMP22 causes severe demyelinating Charcot-Marie-Tooth (CMT) peripheral neuropathy, and duplication of PMP22 causes the most common form of CMT, CMT1A. Yet, the molecular functions provided by PMP22 and how its alteration causes CMT are unknown. Here we find MPZ and PMP22 form a specific complex through interfaces within their transmembrane domains. We also find that the PMP22 A67T patient variant that causes a loss-of-function (Hereditary Neuropathy with Pressure Palsies) phenotype maps to this interface, and blocks MPZ association without affecting localization to the plasma membrane or interactions with other proteins. These data define the molecular basis for the MPZ~PMP22 interaction and indicate this complex fulfills an important function in myelinating cells.

neuroscience↗

bioRxiv2021

ANTH domains within CALM, HIP1R, and Sla2 recognize ubiquitin internalization signals.

Ubiquitin (Ub) serves as a signal for clathrin-mediated endocytosis (CME) by engaging Ub-binding proteins with the internalization apparatus. Ub is a versatile internalization signal because it can be added to a wide variety of membrane proteins, expanding the capacity of cells to use a variety of regulatory mechanisms to specify the conditions under which a particular protein will be internalized. Several candidate adaptors that can recognize ubiquitinated membrane proteins have been identified that work in endocytic processes that are both clathrin-dependent and independent. These include Epsin and Eps15, which bind and help sort Ub-cargo into internalization sites. Here we identify additional components of the endocytosis apparatus that bind Ub. The N-terminal ANTH domains found in CALM, AP180, HIP1R and yeast Sla2 all bind monoubiquitin with {micro}M affinity. ANTH domains belong to a larger superfamily of domains including ENTH and VHS domains, many of which have Ub-binding regions outside of their VHS/ENTH/ANTH domains that enable them to mediate Ub-dependent sorting events throughout the cell. Solution NMR studies combined with a crystal structure of the CALM ANTH domain in a complex with Ub show that Ub binds to a C-terminal region of the ANTH domain that is not present in ENTH domains. Combined loss of Ub-binding by ANTH-domain proteins and other Ub-binding domains within the internalization apparatus of yeast caused defects in the Ub-dependent internalization of the GPCR Ste2 but had no effect on internalization of Ste2 via other internalization signals. These studies define new components of the internalization machinery that work collectively with Epsin and Eps15 to specify recognition of Ub as an internalization signal.

cell biology↗