Biomedical subjects

Hsiangling Teo

Publications and source records attributed to Hsiangling Teo.

5 recordsLinked to original sources

PubMed2007

Structural insight into the ESCRT-I/-II link and its role in MVB trafficking.

ESCRT (endosomal sorting complex required for transport) complexes orchestrate efficient sorting of ubiquitinated transmembrane receptors to lysosomes via multivesicular bodies (MVBs). Yeast ESCRT-I and ESCRT-II interact directly in vitro; however, this association is not detected in yeast cytosol. To gain understanding of the molecular mechanisms of this link, we have characterised the ESCRT-I/-II supercomplex and determined the crystal structure of its interface. The link is formed by the vacuolar protein sorting (Vps)28 C-terminus (ESCRT-I) binding with nanomolar affinity to the Vps36-NZF-N zinc-finger domain (ESCRT-II). A hydrophobic patch on the Vps28-CT four-helix bundle contacts the hydrophobic knuckles of Vps36-NZF-N. Mutation of the ESCRT-I/-II link results in a cargo-sorting defect in yeast. Interestingly, the two Vps36 NZF domains, NZF-N and NZF-C, despite having the same core fold, use distinct surfaces to bind ESCRT-I or ubiquitinated cargo. We also show that a new component of ESCRT-I, Mvb12 (YGR206W), engages ESCRT-I directly with nanomolar affinity to form a 1:1:1:1 heterotetramer. Mvb12 does not affect the affinity of ESCRT-I for ESCRT-II in vitro. Our data suggest a complex regulatory mechanism for the ESCRT-I/-II link in yeast.

Amino Acid Sequence↗

PubMed2007

Structural studies of phosphoinositide 3-kinase-dependent traffic to multivesicular bodies.

Three large protein complexes known as ESCRT I, ESCRT II and ESCRT III drive the progression of ubiquitinated membrane cargo from early endosomes to lysosomes. Several steps in this process critically depend on PtdIns3P, the product of the class III phosphoinositide 3-kinase. Our work has provided insights into the architecture, membrane recruitment and functional interactions of the ESCRT machinery. The fan-shaped ESCRT I core and the trilobal ESCRT II core are essential to forming stable, rigid scaffolds that support additional, flexibly-linked domains, which serve as gripping tools for recognizing elements of the MVB (multivesicular body) pathway: cargo protein, membranes and other MVB proteins. With these additional (non-core) domains, ESCRT I grasps monoubiquitinated membrane proteins and the Vps36 subunit of the downstream ESCRT II complex. The GLUE (GRAM-like, ubiquitin-binding on Eap45) domain extending beyond the core of the ESCRT II complex recognizes PtdIns3P-containing membranes, monoubiquitinated cargo and ESCRT I. The structure of this GLUE domain demonstrates that it has a split PH (pleckstrin homology) domain fold, with a non-typical phosphoinositide-binding pocket. Mutations in the lipid-binding pocket of the ESCRT II GLUE domain cause a strong defect in vacuolar protein sorting in yeast.

Amino Acid Motifs↗

PubMed2006

ESCRT-I core and ESCRT-II GLUE domain structures reveal role for GLUE in linking to ESCRT-I and membranes.

ESCRT complexes form the main machinery driving protein sorting from endosomes to lysosomes. Currently, the picture regarding assembly of ESCRTs on endosomes is incomplete. The structure of the conserved heterotrimeric ESCRT-I core presented here shows a fan-like arrangement of three helical hairpins, each corresponding to a different subunit. Vps23/Tsg101 is the central hairpin sandwiched between the other subunits, explaining the critical role of its "steadiness box" in the stability of ESCRT-I. We show that yeast ESCRT-I links directly to ESCRT-II, through a tight interaction of Vps28 (ESCRT-I) with the yeast-specific zinc-finger insertion within the GLUE domain of Vps36 (ESCRT-II). The crystal structure of the GLUE domain missing this insertion reveals it is a split PH domain, with a noncanonical lipid binding pocket that binds PtdIns3P. The simultaneous and reinforcing interactions of ESCRT-II GLUE domain with membranes, ESCRT-I, and ubiquitin are critical for ubiquitinated cargo progression from early to late endosomes.

Amino Acid Sequence↗

PubMed2004

Structural insights into endosomal sorting complex required for transport (ESCRT-I) recognition of ubiquitinated proteins.

The endosomal sorting complex required for transport (ESCRT-I) is a 350-kDa complex of three proteins, Vps23, Vps28, and Vps37. The N-terminal ubiquitin-conjugating enzyme E2 variant (UEV) domain of Vps23 is required for sorting ubiquitinated proteins into the internal vesicles of multivesicular bodies. UEVs are homologous to E2 ubiquitin ligases but lack the conserved cysteine residue required for catalytic activity. The crystal structure of the yeast Vps23 UEV in a complex with ubiquitin (Ub) shows the detailed interactions made with the bound Ub. Compared with the solution structure of the Tsg101 UEV (the human homologue of Vps23) in the absence of Ub, two loops that are conserved among the ESCRT-I UEVs move toward each other to grip the Ub in a pincer-like grasp. The contacts with the UEV encompass two adjacent patches on the surface of the Ub, one containing several hydrophobic residues, including Ile-8(Ub), Ile-44(Ub), and Val-70(Ub), and the second containing a hydrophilic patch including residues Asn-60(Ub), Gln-62(Ub), Glu-64(Ub). The hydrophobic Ub patch interacting with the Vps23 UEV overlaps the surface of Ub interacting with the Vps27 ubiquitin-interacting motif, suggesting a sequential model for ubiquitinated cargo binding by these proteins. In contrast, the hydrophilic patch encompasses residues uniquely interacting with the ESCRT-I UEV. The structure provides a detailed framework for design of mutants that can specifically affect ESCRT-I-dependent sorting of ubiquitinated cargo without affecting Vps27-mediated delivery of cargo to endosomes.

Amino Acid Motifs↗

PubMed2004

ESCRT-II, an endosome-associated complex required for protein sorting: crystal structure and interactions with ESCRT-III and membranes.

ESCRT-I, -II, and -III protein complexes are sequentially recruited to endosomal membranes, where they orchestrate protein sorting and MVB biogenesis. In addition, they play a critical role in retrovirus budding. Structural understanding of ESCRT interaction networks is largely lacking. The 3.6 A structure of the yeast ESCRT-II core presented here reveals a trilobal complex containing two copies of Vps25, one copy of Vps22, and the C-terminal region of Vps36. Unexpectedly, the entire ESCRT-II core consists of eight repeats of a common building block, a "winged helix" domain. Two PPXY-motifs from Vps25 are involved in contacts with Vps22 and Vps36, and their mutation leads to ESCRT-II disruption. We show that purified ESCRT-II binds directly to the Vps20 component of ESCRT-III. Surprisingly, this binding does not require the protruding N-terminal coiled-coil of Vps22. Vps25 is the chief subunit responsible for Vps20 recruitment. This interaction dramatically increases binding of both components to lipid vesicles in vitro.

Amino Acid Motifs↗