A role of Lck annular lipids in the steady upkeep of active Lck in T cells

Abstract

Theoretical work suggests that collective spatiotemporal behaviour of integral membrane proteins (IMPs) can be modulated by annular lipids sheathing their hydrophobic moiety. Here, we present evidence for this prediction in a natural membrane by investigating the mechanism that maintains steady amount of active isoform of Lck kinase (LckA) by Lck trans-autophosphorylation offset by the phosphatase CD45. We gauged experimental suitability by quantitation of CD45 and LckA subcellular localisation, LckA generation as a function of Lck and pharmacological perturbation. Steady LckA was challenged by swapping Lck membrane anchor with structurally divergent ones expected to substantially modify Lck annular lipids, such as that of Src or the transmembrane domains of LAT, CD4, palmitoylation-defective CD4 and CD45, respectively. The data showed only small alteration of LckA, except for CD45 hydrophobic anchor that thwarted LckA, due to excessive lateral proximity to CD45. The data are best explained by annular lipids facilitating or penalising IMPs' lateral proximity, hence modulating IMPs protein-protein functional interactions. Our findings can contribute to improve the understanding of biomembranes' organisation.

Molecular dynamics simulations reveal membrane lipid interactions of the full-length lymphocyte specific kinase (Lck)

“…Upon binding to the membrane, we show that the full-length Lck is surrounded by a pool of negatively charged lipid headgroups creating an anionic environment, whereas it is also observed that the TCR-CD3 cytoplasmic tails maintain an anionic lipid environment 18 . This sheds light on the potential significance of lipids during TCR-Lck association 19 .…”

“…Lck was also shown to possess high affinity for PIP lipids 16 and its clustering is driven by their open conformational state 6 . However, lateral interactions of Lck molecules may also include other Lck isoforms as suggested by a recent study 19 . Nevertheless, it is important to understand how the open and closed states of Lck interact with the membrane in molecular detail.…”