Flotillins are the major structural proteins in erythroid raft domains. We have shown previously that the dynamic nanoscale organization of raft domains in erythroid cells may depend on flotillin-MPP1 interactions. Here, by using molecular dynamic simulations and a surface plasmon resonance-based approach we determined that high-affinity complexes of MPP1 and flotillins are formed via a so far unidentified region within the D5 domain of MPP1. Significantly, this particular “flotillin binding motif” is of key physiological importance, as overexpression of peptides containing this motif inhibited endogenous MPP1-flotillin interaction in erythroid precursor cells, thereby causing lateral disorganization of raft domains.
Fig: Structure of MPP1. Schematic representation (a) of the overall domain composition and ribbon model (b) of the structure of MPP1. PDZ blue, SH3 green, D5 light blue, GUK red. Domain boundaries were marked based on Quinn et al.. Structural model redrawn according to Listowski et al.
This was reflected by both reduction in the plasma membrane order and markedly decreased activation of signal transduction via the raft-dependent insulin receptor pathway. Our data highlight new molecular details concerning the mechanism whereby MPP1 functionally links flotillins to exert their physiological role in raft domain formation.
Biernatowska, A., Olszewska, P., Grzymajło, K. et al. Molecular characterization of direct interactions between MPP1 and flotillins. Sci Rep 11, 14751 (2021). https://doi.org/10.1038/s41598-021-93982-3