Abstract
MPP1 (membrane palmitoylated protein 1) belongs to the MAGUK (membrane-associated guanylate kinase homologs) scaffolding protein family. These proteins organize molecules into complexes, thereby maintaining the structural heterogeneity of the plasma membrane (PM). Our previous results indicated that direct, high-affinity interactions between MPP1 and flotillins (raft marker proteins) display dominant PM-modulating capacity in erythroid cells. In this study, with high-resolution structured illuminated imaging, we investigated how these complexes are organized within erythroid cells on the nanometer scale. Furthermore, using other spectroscopic techniques, namely fluorescence recovery after photobleaching (FRAP) and spot-variation fluorescence correlation spectroscopy (svFCS), we revealed that MPP1 acts as a key raft-capturing molecule, regulating temporal immobilization of flotillin-based nanoclusters, and controls local concentration and confinement of sphingomyelin and Thy-1 in raft nanodomains. Our data enabled us to uncover molecular principles governing the key involvement of MPP1-flotillin complexes in the dynamic nanoscale organization of PM of erythroid cells.
Highlights
According to well-established knowledge, plasma membrane (PM) consists of many coexisting domains, heterogeneous and dynamic in nature and size, whose composition varies among cell types and determines their sophisticated functions
Our recent research showed that high-affinity complexes of MPP1 and flotillins functionally control the lateral organization of PM in erythroid cells [8,9]
Determination of factors regulating the self-organization and stability of raft nanodomains is a key issue considering their crucial impact in spatiotemporal organization of PM and involvement in the regulation of numerous cellular processes, especially those related to cancer progression [27]
Summary
According to well-established knowledge, PM consists of many coexisting domains, heterogeneous and dynamic in nature and size (from nano- to microdomains), whose composition varies among cell types and determines their sophisticated functions. From the perspective of the PM organization, raft nanodomains might be considered as functional, small building blocks, enabling the construction of larger microdomains and contributing to the spatiotemporal compartmentalization of the PM. In this particular context, raft nanodomain organization/formation has to be tightly coordinated. The outstanding question, is which biological factors might determine the self-organizing capacity and local stability of the existing raft nanodomains at the PM and whether such a mechanism(s) might occur as a general rule for different cell types
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