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Biomedical subjects

Rachel Errington

Publications and source records attributed to Rachel Errington.

4 recordsLinked to original sources
PubMed2004

Endophilin A3 forms filamentous structures that colocalise with microtubules but not with actin filaments.

Endophilin A3 is a member of the endophilin family of proteins, thought to play a role in the formation of clathrin-coated vesicles from the plasma membrane in the process of clathrin-mediated endocytosis. We investigated the localisation of both endogenous and overexpressed endophilin A3 within mammalian cells. Endophilin A3 demonstrated a complex cellular distribution with bright punctate structures and filamentous strands superimposed on a diffuse cytoplasmic background. The endophilin A3 structures did not colocalise with mitochondria, endoplasmic reticulum or lysosomes. Direct immunolocalisation and cytoskeletal perturbation studies showed that the filamentous structures were more likely to be colocalised with microtubules than actin filaments. We therefore propose that endophilin A3 has a role in transport along or as part of the structure of microtubules, in addition to its suggested role in endocytosis.

Actin Cytoskeleton↗
PubMed2004

Identification of sequences required for the import of human protoporphyrinogen oxidase to mitochondria.

Protoporphyrinogen oxidase (PPOX; EC 1.3.3.4), the penultimate enzyme of haem biosynthesis, is a nucleus-encoded flavoprotein strongly associated with the outer surface of the inner mitochondrial membrane. It is attached to this membrane by an unknown mechanism that appears not to involve a membrane-spanning domain. The pathway for its import to mitochondria and insertion into the inner membrane has not been established. We have fused human PPOXs containing N-terminal deletions, C-terminal deletions or missense mutations to yellow fluorescent protein (YFP) and have used these constructs to investigate the mitochondrial import of PPOX in human cells. We show that all the information required for efficient import is contained within the first 250 amino acid residues of human PPOX and that targeting to mitochondria is prevented by fusion of YFP to the N-terminus. Deletion of between 151 and 175 residues from the N-terminus is required to abolish import, whereas shorter deletions impair its efficiency. Fully efficient targeting appears to require both a major targeting signal, the whole or part of which is contained between residues 151 and 175, and which may be involved in anchoring to the inner mitochondrial membrane, together with interaction between this region and a sequence(s) within the first 150 residues. These features suggest that the mechanism for import of human PPOX to mitochondria differs from those identified for the translocation of nucleus-encoded, membrane-spanning, inner membrane proteins. In addition, a missense mutation outside this region (Val(335)-->Gly) prevented targeting to mitochondria and delayed the appearance of YFP fluorescence. This mutation appeared to prevent import by a direct effect on protein folding rather than by altering a sequence required for targeting. It may lead to sequestration of the PPOX-YFP construct in an unfolded conformation, followed by proteolytic degradation, possibly through enhanced binding to a cytosolic chaperone protein.

Amino Acid Sequence↗
PubMed2003

Solid-phase synthesis of the cyclic peptide portion of chlorofusin, an inhibitor of p53-MDM2 interactions.

The first solid-phase synthesis of the chlorofusin peptide is described. The synthesis involved side-chain immobilization of N(alpha)-Fmoc-Asp-ODmab. Synthesis of the linear peptide, initially incorporating racemic Ade8 and unsubstituted ornithine in place of the chromophore-bearing residue, was followed by cyclization on resin and peptide release to give a mixture of diastereomers. Resynthesis identified (by HPLC) the second isomer as analogous to the natural product. Initial biological assays, using an immunofluorescence method, suggest that the compounds are not cytotoxic but do not inhibit the p53/mdm2 interaction. [structure: see text]

Antineoplastic Agents↗