https://www.cell.com/trends/cell-biology/pdf/S0962-8924(09)00139-1.pdf

Tetraspanin-enriched Microdomains: A Functional Unit in Cell Plasma Membranes

Elements of the cytoskeleton interact intimately and communicate bidirectionally with cellular membranes. Such interactions are critical for a host of cellular processes. Here we focus on the many types of interactions that exist between the cytoskeleton and the plasma membrane to illustrate why these cellular components can never truly be studied in isolation in vivo. We discuss how membranecytoskeleton interactions are mediated and modulated, and how many proteins involved in these interactions are disrupted in human disease. We then highlight key molecular and physical variables that must be considered in order to mechanistically dissect events associated with changes in plasma membrane morphology. These considerations are integrated into the context of cell migration, filopodia formation, and clathrin-mediated endocytosis to show how a holistic view of the plasma membrane-cytoskeleton interface can allow for the appropriate interpretation of experimental findings and provide novel mechanistic insight into these important cellular events.

/pdf/mediation-modulation-and-consequences-of-membrane-1iv5hy4jpa.pdf

Mediation, Modulation, and Consequences of Membrane-Cytoskeleton Interactions

Flotillins are membrane proteins that form microdomains in the plasma membrane of all mammalian cell types studied to date. They span the evolutionary spectrum, with proteins related to flotillins present in bacteria, fungi, plants and metazoans, which suggests that they perform important, and probably conserved, functions. Flotillins have been implicated in myriad processes that include endocytosis, signal transduction and regulation of the cortical cytoskeleton, yet the molecular mechanisms that underlie flotillin function in these different cases are still poorly understood. In this Commentary, we will provide an introduction to these intriguing proteins, summarise their proposed functions and discuss in greater detail some recent insights into the role of flotillin microdomains in endocytosis that have been provided by several independent studies. Finally, we will focus on the questions that are raised by these new experiments and their implications for future studies.

/pdf/the-roles-of-flotillin-microdomains-endocytosis-and-beyond-11sqye1wzf.pdf

The roles of flotillin microdomains - endocytosis and beyond

Endocytosis is essential for the maintenance of protein and lipid compositions in the plasma membrane and for the acquisition of materials from the extracellular space. Clathrin-dependent and -independent endocytic processes are well established in yeast and animals; however, endocytic pathways involved in cargo internalization and intracellular trafficking remain to be fully elucidated for plants. Here, we used transgenic green fluorescent protein–flotillin1 (GFP-Flot1) Arabidopsis thaliana plants in combination with confocal microscopy analysis and transmission electron microscopy immunogold labeling to study the spatial and dynamic aspects of GFP-Flot1–positive vesicle formation. Vesicle size, as outlined by the gold particles, was ;100 nm, which is larger than the 30-nm size of clathrin-coated vesicles. GFP-Flot1 also did not colocalize with clathrin light chainmOrange. Variable-angle total internal reflection fluorescence microscopy also revealed that the dynamic behavior of GFPFlot1–positive puncta was different from that of clathrin light chain-mOrange puncta. Furthermore, disruption of membrane microdomains caused a significant alteration in the dynamics of Flot1-positive puncta. Analysis of artificial microRNA Flot1 transgenic Arabidopsis lines established that a reduction in Flot1 transcript levels gave rise to a reduction in shoot and root meristem size plus retardation in seedling growth. Taken together, these findings support the hypothesis that, in plant cells, Flot1 is involved in a clathrin-independent endocytic pathway and functions in seedling development.

/pdf/a-membrane-microdomain-associated-protein-arabidopsis-flot1-2b5jqj7odh.pdf

A membrane microdomain-associated protein, Arabidopsis Flot1, is involved in a clathrin-independent endocytic pathway and is required for seedling development.

Eukaryotic plasma membranes are highly compartmentalized structures. So far, only a few individual proteins that function in a wide range of cellular processes have been shown to segregate into microdomains. However, the biological roles of most microdomain-associated proteins are unknown. Here, we investigated the heterogeneity of distinct microdomains and the complexity of their coexistence. This diversity was determined in living cells of intact multicellular tissues using 20 different marker proteins from Arabidopsis thaliana, mostly belonging to the Remorin protein family. These proteins associate with microdomains at the cytosolic leaflet of the plasma membrane. We characterized these membrane domains and determined their lateral dynamics by extensive quantitative image analysis. Systematic colocalization experiments with an extended subset of marker proteins tested in 45 different combinations revealed the coexistence of highly distinct membrane domains on individual cell surfaces. These data provide valuable tools to study the lateral segregation of membrane proteins and their biological functions in living plant cells. They also demonstrate that widely used biochemical approaches such as detergent-resistant membranes cannot resolve this biological complexity of membrane compartmentalization in vivo.

/pdf/plasma-membranes-are-subcompartmentalized-into-a-plethora-of-3xx0d0eyae.pdf

Plasma Membranes Are Subcompartmentalized into a Plethora of Coexisting and Diverse Microdomains in Arabidopsis and Nicotiana benthamiana

https://febs.onlinelibrary.wiley.com/doi/epdf/10.1016/j.febslet.2007.08.074

Sylvia Hannbeck

Papers

Linking membrane microdomains to the cytoskeleton: regulation of the lateral mobility of reggie-1/flotillin-2 by interaction with actin.