MPP1 directly interacts with flotillins in erythrocyte membrane - Possible mechanism of raft domain formation

Abstract

Flotillins are prominent, oligomeric protein components of erythrocyte (RBC) membrane raft domains and are considered to play an important structural role in lateral organization of the plasma membrane. In our previous work on erythroid membranes and giant plasma membrane vesicles (GPMVs) derived from them we have shown that formation of functional domains (resting state rafts) depends on the presence of membrane palmitoylated protein 1 (MPP1/p55), pointing to its new physiological role. Exploration of the molecular mechanism of MPP1 function in organizing membrane domains described here, through searching for its molecular partners in RBC membrane by using different methods, led to the identification of the raft-marker proteins, flotillin 1 and flotillin 2, as hitherto unreported direct MPP1 binding-partners in the RBC membrane. These proteins are found in high molecular-weight complexes in native RBC membrane and, significantly, their presence was shown to be separate from the well-known protein 4.1-dependent interactions of MPP1 with membrane proteins. Furthermore, FLIM analysis revealed that loss of the endogenous MPP1-flotillins interactions resulted in significant changes in RBC membrane-fluidity, emphasizing the physiological importance of such interactions in vivo. Therefore, our data establish a new perspective on the role of MPP1 in erythroid cells and suggests that direct MPP1-flotillins interactions could be the major driving-force behind the formation of raft domains in RBC.

Flotillins: At the Intersection of Protein S-Palmitoylation and Lipid-Mediated Signaling

“…Another line of data supporting a relation of flotillins with rafts come from immunofluorescence and electron microscopy studies, indicating partial co-localization of flotillins and GPI-anchored proteins after their clustering [18,35,84,94]. Moreover, recent studies of the Sikorski's group have indicated that flotillins interact with another S-palmitoylated raft-associated protein-MPP1 of the membrane-associated guanylate kinase (MAGUK) family of scaffolding proteins-and together they contribute to the assembly of rafts in the erythrocyte membrane [66,82].…”

“…In breast cancer cells, flotillins stabilize ErbB2 in the plasma membrane sustaining signaling activity [106]. In erythrocytes, flotillins contribute to the organization of membrane rafts in co-operation with MPP1 protein [66,82,107]. Thus, it can be proposed that flotillins bound to the inner leaflet of the plasma membrane facilitate the assembly of plasma membrane microregions originating from rafts.…”

Functional Characterization of Plasmodium falciparum Surface-Related Antigen as a Potential Blood-Stage Vaccine Target

“…Ethical approval was obtained from the ethics committees as documented previously [16,17]. Immunoreactivity screenings of plasma samples were performed by enzyme-linked immunosorbent assay (ELISA) [12] and immuno-dot blotting [18] using the synthetic peptides PfSRA P1 (NNKDNHNKKDTNENC); PfSRA P2 (CENDNDEYGNKNKNS); and PfSRA P3 (CSNNKKKKK NDKKKK). R1 peptide (LFSKFGSRMHILKC) was used as control (R1 peptide blocks AMA 1-RON 4 interaction), and naive plasma was used as negative control.…”

Outcome and impact of post‐remission strategy after MIDAM regimen in patients with relapsing or refractory acute myeloid leukemia

“…6 In a univariate analysis related to age, this study revealed no significant difference in CR between the different age groups, and the results suggest that the MIDAM regimen could be an acceptable choice as salvage treatment in the elderly. 6 In a univariate analysis related to age, this study revealed no significant difference in CR between the different age groups, and the results suggest that the MIDAM regimen could be an acceptable choice as salvage treatment in the elderly.…”

“…GO in fractionated doses has been shown to be highly effective in association with chemotherapy and could be an interesting option in our MIDAM regimen because this approach allows the delivery of high cumulative doses without excessive toxicity. 6 In a univariate analysis related to age, this study revealed no significant difference in CR between the different age groups, and the results suggest that the MIDAM regimen could be an acceptable choice as salvage treatment in the elderly. Induction-related death was linked to performance status, with no significant influence of age.…”