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First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Mathias Cobbaut and Ahmed Elbediwy are co-first authors on ‘The Rho family GEF FARP2 is activated by aPKCι to control tight junction formation and polarity’, published in JCS. Mathias is a postdoc in the lab of Prof. Peter Parker at The Francis Crick Institute, London, investigating protein kinase regulation/biochemistry and the functional role of protein kinase signaling. Ahmed is a lecturer at Kingston University, investigating cancer biology, polarity and signaling.

The elaboration of polarity is central to organismal development and to the maintenance of functional epithelia. Amongst the controls determining polarity are the PAR proteins, PAR6/aPKCι/PAR3, regulating both known and unknown effectors. Here we identify FARP2 as a "RIPR" motif dependent partner and substrate of aPKCι that is required for efficient polarisation and junction formation. Binding is conferred by a FERM/FA domain-Kinase domain interaction and detachment promoted by aPKCι dependent phosphorylation. FARP2 is shown to promote GTP loading of Cdc42 consistent with upstream regulation of the polarising PAR6-aPKCι complex. However, it is shown that aPKCι acts to promote the localised activity of FARP2 through phosphorylation. We conclude that this aPKCι−FARP2 complex formation acts as a positive feedback control to drive polarisation through aPKCι and other Cdc42 effectors

First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Ahmed Elbediwy is the first author on ‘Enigma proteins regulate YAP mechanotransduction’, published in Journal of Cell Science. Ahmed is a postdoctoral fellow in the lab of Barry Thompson at The Francis Crick Institute, London, UK, investigating the cytoskeleton, RhoGTPases and the regulation of YAP/TAZ oncoproteins.

In epithelial tissues, polarisation of microtubules and actin microvilli occurs along the apical-basal axis of each cell, yet how these cytoskeletal polarisation events are coordinated remains unclear. Here, we examine the hierarchy of events during cytoskeletal polarisation in Drosophila melanogaster epithelia. Core apical-basal polarity determinants polarise the spectrin cytoskeleton to recruit the microtubule-binding proteins Patronin (CAMSAP1, CAMSAP2 and CAMSAP3 in humans) and Shortstop [Shot; MACF1 and BPAG1 (also known as DST) in humans] to the apical membrane domain. Patronin and Shot then act to polarise microtubules along the apical-basal axis to enable apical transport of Rab11 endosomes by the Nuf-Dynein microtubule motor complex. Finally, Rab11 endosomes are transferred to the MyoV (also known as Didum in Drosophila) actin motor to deliver the key microvillar determinant Cadherin 99C to the apical membrane to organise the biogenesis of actin microvilli.