Search bioRxiv⌕ Search

Biology subjects

Barcelona, B.

Publications and source records attributed to Barcelona, B..

2 recordsLinked to original sources

Drebrin forms a cortical hub that connects actin, microtubules, and clathrin for endocytic transport of β2 integrin

Using primary human macrophages, we analyze the molecular machinery that enables direct contact of microtubule +tips with podosomes, and its connection to clathrin-based endocytosis. We show that the podosome cap protein drebrin, together with its +tip-localized binding partner EB3, regulates podosome-microtubule contact. Importantly, drebrin depletion leads to reduced endocytosis, particularly of {beta}2 integrin at podosomes. This is based on drebri[n]s interaction with {beta}2 integrin, and its direct binding of clathrin heavy chain via a canonical clathrin box and a novel box, which we identify also in other mammalian proteins. Our data enable a model of the molecular machinery that regulates direct contact between podosomes and microtubule +tips. Moreover, we provide evidence for spatial selectivity in endocytosis of {beta} integrins, while also revealing a more general principle of endocytic trafficking regulation, through drebrin working as a multivalent, actin-based hub that links the clathrin system with microtubule-based transport.

cell biology↗

Allosteric deregulation of phenylalanine biosynthesis evolved with the emergence of vascular plants

Phenylalanine (Phe) is the precursor of essential secondary products in plants. Here we show that a key, rate-limiting step in Phe biosynthesis, which is catalyzed by arogenate dehydratase (ADT), experienced allosteric de-regulation during evolution. Enzymes from microorganisms and type-I ADTs from plants are strongly feedback-inhibited by Phe, while type-II isoforms remain active at high levels of Phe. We have found that type-II ADTs are widespread across seed plants and their overproduction resulted in a dramatic accumulation of Phe in planta, up to 40-times higher than those observed following the expression of type-I enzymes. Punctual changes in the allosteric binding site of Phe and adjacent region are responsible for the observed relaxed regulation. The phylogeny of plant ADTs evidences that the emergence of type-II isoforms with relaxed regulation occurred at some point in the transition between non-vascular plants and tracheophytes enabling the massive production of Phe-derived compounds, primarily lignin, which are attributes of vascular plants.

plant biology↗