Intermembrane protein transfer. Band 3, the erythrocyte anion transporter, transfers in native orientation from human red blood cells into the bilayer of phospholipid vesicles

Transfer of membrane(s) matter(s)-non-genetic inheritance of (metabolic) phenotypes?

Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are anchored at the outer phospholipid layer of eukaryotic plasma membranes exclusively by a glycolipid. GPI-APs are not only released into extracellular compartments by lipolytic cleavage. In addition, certain GPI-APs with the glycosylphosphatidylinositol anchor including their fatty acids remaining coupled to the carboxy-terminus of their protein components are also detectable in body fluids, in response to certain stimuli, such as oxidative stress, radicals or high-fat diet. As a consequence, the fatty acid moieties of GPI-APs must be shielded from access of the aqueous environment by incorporation into membranes of extracellular vesicles or into micelle-like complexes together with (lyso)phospholipids and cholesterol. The GPI-APs released from somatic cells and tissues are transferred via those complexes or EVs to somatic as well as pluripotent stem cells with metabolic consequences, such as upregulation of glycogen and lipid synthesis. From these and additional findings, the following hypotheses are developed: i) Transfer of GPI-APs via EVs or micelle-like complexes leads to the induction of new phenotypes in the daughter cells or zygotes, which are presumably not restricted to metabolism. ii) The membrane topographies transferred by the concerted action of GPI-APs and interacting components are replicated by self-organization and self-templation and remain accessible to structural changes by environmental factors. iii) Transfer from mother cells and gametes to their daughter cells and zygotes, respectively, is not restricted to DNA and genes, but also encompasses non-genetic matter, such as GPI-APs and specific membrane constituents. iv) The intergenerational transfer of membrane matter between mammalian organisms is understood as an epigenetic mechanism for phenotypic plasticity, which does not rely on modifications of DNA and histones, but is regarded as molecular mechanism for the inheritance of acquired traits, such as complex metabolic diseases. v) The missing interest in research of non-genetic matter of inheritance, which may be interpreted in the sense of Darwin's "Gemmules" or Galton's "Stirps", should be addressed in future investigations of the philosophy of science and sociology of media.

(Patho)Physiology of Glycosylphosphatidylinositol-Anchored Proteins II: Intercellular Transfer of Matter (Inheritance?) That Matters

Glycosylphosphatidylinositol (GPI)-anchored proteins (APs) are anchored at the outer leaflet of the plasma membrane (PM) bilayer by covalent linkage to a typical glycolipid and expressed in all eukaryotic organisms so far studied. Lipolytic release from PMs into extracellular compartments and intercellular transfer are regarded as the main (patho)physiological roles exerted by GPI-APs. The intercellular transfer of GPI-APs relies on the complete GPI anchor and is mediated by extracellular vesicles such as microvesicles and exosomes and lipid-free homo- or heteromeric aggregates, and lipoprotein-like particles such as prostasomes and surfactant-like particles, or lipid-containing micelle-like complexes. In mammalian organisms, non-vesicular transfer is controlled by the distance between donor and acceptor cells/tissues; intrinsic conditions such as age, metabolic state, and stress; extrinsic factors such as GPI-binding proteins; hormones such as insulin; and drugs such as anti-diabetic sulfonylureas. It proceeds either "directly" upon close neighborhood or contact of donor and acceptor cells or "indirectly" as a consequence of the induced lipolytic release of GPI-APs from PMs. Those displace from the serum GPI-binding proteins GPI-APs, which have retained the complete anchor, and become assembled in aggregates or micelle-like complexes. Importantly, intercellular transfer of GPI-APs has been shown to induce specific phenotypes such as stimulation of lipid and glycogen synthesis, in cultured human adipocytes, blood cells, and induced pluripotent stem cells. As a consequence, intercellular transfer of GPI-APs should be regarded as non-genetic inheritance of (acquired) features between somatic cells which is based on the biogenesis and transmission of matter such as GPI-APs and "membrane landscapes", rather than the replication and transmission of information such as DNA. Its operation in mammalian organisms remains to be clarified.

Application and Utility of Liposomal Neuroprotective Agents and Biomimetic Nanoparticles for the Treatment of Ischemic Stroke

Ischemic stroke is still one of the leading causes of high mortality and severe disability worldwide. Therapeutic options for ischemic stroke and subsequent cerebral ischemia/reperfusion injury remain limited due to challenges associated with drug permeability through the blood-brain barrier (BBB). Neuroprotectant delivery with nanoparticles, including liposomes, offers a promising solution to address this problem, as BBB disruption following ischemic stroke allows nanoparticles to pass through the intercellular gaps between endothelial cells. To ameliorate ischemic brain damage, a number of nanotherapeutics encapsulating neuroprotective agents, as well as surface-modified nanoparticles with specific ligands targeting the injured brain regions, have been developed. Combination therapy with nanoparticles encapsulating neuroprotectants and tissue plasminogen activator (t-PA), a globally approved thrombolytic agent, has been demonstrated to extend the narrow therapeutic time window of t-PA. In addition, the design of biomimetic drug delivery systems (DDS) employing circulating cells (e.g., leukocytes, platelets) with unique properties has recently been investigated to overcome the injured BBB, utilizing these cells’ inherent capability to penetrate the ischemic brain. Herein, we review recent findings on the application and utility of nanoparticle DDS, particularly liposomes, and various approaches to developing biomimetic DDS functionalized with cellular membranes/membrane proteins for the treatment of ischemic stroke.

Leukocyte-Mimetic Liposomes Penetrate Into Tumor Spheroids and Suppress Spheroid Growth by Encapsulated Doxorubicin

As leukocytes can penetrate into deep regions of a tumor mass, leukocyte-mimetic liposomes (LM-Lipo) containing leukocyte membrane proteins are also expected to penetrate into tumors by exerting properties of those membrane proteins. The aim of the present study was to examine whether LM-Lipo, which were recently demonstrated to actively pass through inflamed endothelial layers, can penetrate into tumor spheroids, and to investigate the potential of LM-Lipo for use as an anticancer drug carrier. We prepared LM-Lipo via intermembrane protein transfer from human leukemia cells; transfer of leukocyte membrane proteins onto the liposomes was determined by Western blotting. LM-Lipo demonstrated a significantly high association with human lung cancer A549 cells compared with plain liposomes, which contributed to effective anti-proliferative action by encapsulated doxorubicin hydrochloride (DOX). Confocal microscopic images showed that LM-Lipo, but not plain liposomes, could efficiently penetrate into A549 tumor spheroids. Moreover, DOX-encapsulated LM-Lipo significantly suppressed tumor spheroid growth. Thus, leukocyte membrane proteins transferred onto LM-Lipo retained their unique function, which allowed for efficient penetration of the liposomes into tumor spheroids, similar to leukocytes. In conclusion, these results suggest that LM-Lipo could be a useful tumor-penetrating drug delivery system for cancer treatment.

[Development of DDS Actively to Overcome the Blood-brain Barrier in the Region of Ischemic Stroke]

We previously showed that increased permeability of the blood-brain barrier (BBB) after ischemic stroke enables extravasation of nano-sized liposomes and accumulation in the ischemic region, and that delivery of neuroprotective agents using liposomal drug delivery systems (DDS) is applicable for treating cerebral ischemia/reperfusion (I/R) injury. However, entry of liposomes into the brain parenchyma was limited in the early stages after I/R possibly due to microvascular dysfunction induced by pathological progression. As such, new approaches to overcome the BBB are needed. Leukocytes can pass through inflamed BBB in I/R region due to membrane proteins displayed on their surface. We thus hypothesized that incorporation of leukocyte membrane proteins onto liposomal membranes would impart leukocyte-mimicking functions to liposomes and that leukocyte-mimetic liposomes (LM-Lipo) may pass through inflamed endothelial cells and BBB, similar to leukocytes. LM-Lipo prepared using intermembrane protein transfer from human leukemia cells showed significantly increased association to inflamed human umbilical vein endothelial cells relative to plain liposomes. Moreover, LM-Lipo passed through inflamed endothelial cell layer by regulating intercellular junctions. These results suggest that imparting leukocyte-like properties to liposomes via intermembrane protein transfer would be an effective strategy to overcome inflamed endothelial barriers. In this review, we describe our findings on ischemic stroke treatment using liposomal DDS and the potential of LM-Lipo to overcome inflamed endothelial barriers.

Relocation of active acetylcholinesterase to liposome–gel conjugate

Relocation of a glycosylphosphatidylinositol (GPI)-anchored protein acetylcholinesterase (AChE) in its enzymatically active form from proteovesicles containing human erythrocyte ghost membrane proteins onto a liposome-gel conjugate was examined. Liposomes of 1,2-dimyristoylphosphatidylcholine (DMPC) were immobilized on Sephacryl S-1000 gel that was chemically modified to bear hydrophobic octyl moieties. Upon coincubation of the liposome-gel conjugate with freely suspended proteovesicles prepared from erythrocyte ghosts, 50% of the AChE left the proteovesicles and immobilized onto the liposome-gel conjugate in 18 h. When the proteovesicles were immobilized and interacted with freely suspended plain liposomes, approximately 2% of the AChE appeared in the liposome fraction. The relocation of AChE apparently possesses strong preference for the liposome-gel conjugate, suggesting that the hydrophobic moieties on the gel could assist the relocation.

GPI-linked proteins do not transfer spontaneously from erythrocytes to liposomes. New aspects of reorganization of the cell membrane

Exposure of cells to liposomes results in the release of integral membrane proteins. However, it is still controversial whether the release is due to spontaneous protein transfer from cells to liposomes or shed vesicles released from cells. We investigated this issue in an erythrocyte-liposome system by examining the location of acetylcholinesterase (AChE, an integral membrane protein marker), cholesterol (erythrocyte membrane lipid marker), hemoglobin (cytosolic protein marker), and a nonexchangeable lipid marker in liposomes in a sucrose density gradient at high resolution. The density distribution showed that AChE is not transferred to the liposomes but is located on small (about 50 nm) light (10-20 wt % sucrose) or large (about 200 nm) heavy shed vesicles (more than 30 wt % sucrose). AChE in the light shed-vesicle fraction markedly increased even after its level in the heavy fraction reached a plateau. AChE was also released from isolated heavy shed vesicles and accumulated in the small light shed-vesicle fraction in the presence of liposomes. After incubation of spherical erythrocytes (morphological index, 5.0) with liposomes, AChE hardly appeared in the heavy shed-vesicle fraction, and the majority (>99%) appeared in the light shed-vesicle fraction, indicating that AChE is released from both the erythrocytes and heavy shed vesicles to the light shed-vesicle fraction, which becomes rich in AChE. Our results demonstrated for the first time that GPI-linked proteins do not spontaneously transfer from erythrocytes to liposomes. Our study also suggests that in vivo GPI-linked membrane proteins do not spontaneously transfer between cell membranes but that some catalyst is needed.

Effect of dicetylphosphate or stearic acid on spontaneous transfer of protein from influenza virus-infected cells to dimyristoylphosphatidylcholine liposomes

Membrane proteins, such as viral spike, were transferred spontaneously from influenza virus-infected cells to various liposomes. The protein transfer was enhanced by the presence of negative charged component dicetylphosphate (DCP) or stearic acid (SA) in dimyristoylphosphatidylcholine (DMPC) liposomes. The lowering of membrane fluidity did not relate to the effect of DCP or SA on protein transfer in this study. We considered that the alteration of membrane properties, such as construction of the surface or stability of transferred protein in liposomes, due to the specific structure of DCP or SA is responsible for the enhancement of spontaneous protein transfer by the presence of the amphiphilic components.

Direct extraction of A and B blood group antigens from human red cells by liposomes

BACKGROUND

Some of the major blood group antigens are on lipids and proteins of the red cell membrane. Incubation of intact red cells with liposomes containing specially designed artificial lipids has been shown to result in the extraction of membrane proteins by the liposomes. The extraction of blood group structures and the retention of their antigenicity have not been reported.

STUDY DESIGN AND METHODS

After the incubation of red cells with liposomes, the extraction of the antigens from human red cells by liposomes was examined by evaluation of the agglutination of the liposomes by respective antisera.

RESULTS

Agglutination specific to the A and B blood group antigens was seen, which indicated that the antigenicity of the blood group antigens was retained even after the extraction by the liposomes. The presence of an artificial boundary lipid, 1,2-dimyristamido-1,2-deoxyphosphatidylcholine, in the liposome was crucial to the efficient extraction of the A and B antigens. On the other hand, the extraction of D, M, N, and P1 was not always detectable by agglutination.

CONCLUSION

The A and B blood group antigens were directly extracted from red cells by liposomes without loss of antigenicity.

Liposomes bearing platelet proteins: a model for surface functions studies

An improved procedure for the direct transfer of membrane proteins from human platelets to liposomes involving the treatment of platelets with linolenic acid was developed. The transfer of platelet proteins to liposomes prepared from the mixture of L-alpha-dimyristoyl-phosphatidylcholine/sphingomyelin in the molar ratio 80/20 appeared to be significantly enhanced compared with liposomes prepared from the same components mixed in other ratios. A wide range of platelet proteins was transferred, the most important being GPIb (170 kDa), GPIIb/IIIa (135 and 110 kDa). GPIV (90 kDa), GPIX (24 kDa) and the serotonin transporter (68 kDa). The recognition interactions between these proteoliposomes and specific protein antibodies clearly indicate that the non-invasive procedure used in this study ensured the reproducible transfer of platelet proteins without essentially altering their original conformation. The obtained results reveal also that the affinity of proteoliposomes to bind paroxetin was virtually the same as that of the native serotonin transporter. These results provide an indication of the possible use of such proteoliposomes as models to study at the molecular level the interaction of these proteins with their ligands.

Physical determinants of intermembrane protein transfer

Intermembrane protein transfer between erythrocytes and phospholipid vesicles was examined under a variety of conditions to investigate physical factors governing this process. Human erythrocytes were incubated with sonicated dimyristoylphosphatidylcholine vesicles containing trace [14C]dipalmitoylphosphatidylcholine. Protein-vesicle complexes were separated from cells and from membrane fragments by density gradient centrifugation. The yield of isolated protein vesicles was determined from the 14C-vesicle marker; protein compositions were analyzed by SDS-polyacrylamide gel electrophoresis. Enzymatic removal of portions of the cytoplasmic or exoplasmic domains of cell membrane proteins had little effect on the extent of protein transfer. Membrane additives such as cholate produced a 2-fold increase in protein-vesicle yield. The selectivity of protein transfer from erythrocytes was influenced by the lipid composition of recipient vesicles: inclusion of cholesterol increased band 3 content while the presence of anionic phospholipids reduced transfer. Proteins transferred from 32P-labeled cells differed in specific radioactivity from bulk cell proteins: glycophorin, highly phosphorylated in the cell membrane, showed no detectable labeling in the corresponding protein-vesicle band. These observations suggest that cell-to-vesicle protein transfer is insensitive to bulk steric and electrostatic properties of cell membranes, but enhanced by membrane defects. Recipient membrane composition influences the selectivity of transferred proteins and may reveal subtle differences in the membrane association of protein subpopulations.

Wheat germ agglutinin stabilization of erythrocyte shape: role of bilayer balance and the membrane skeleton

The effects of wheat germ agglutinin (WGA), Limulus lectin, and concanavalin A on cell shape changes were examined in human erythrocytes. These agents inhibited echinocytosis in cells having elevated cytosolic Ca2+ or incorporated foreign phosphatidylcholine, but had no effect on cell stomatocytosis in response to incorporated phosphatidylserine. The role of the membrane skeleton in this selective membrane fixation was examined. WGA inhibited echinocytosis in cells previously depleted of polyphosphoinositides to reduce membrane skeleton binding to transmembrane proteins, treated with phorbol ester to enhance protein 4.1 phosphorylation, heat-treated to denature spectrin, alkylated with p-chloromercuribenzoate to dissociate glycophorin from the membrane skeleton, or subjected to elevated cell 2,3-diphosphoglycerate to alter organization of the spectrin-actin-protein 4.1 complex. Limulus lectin and increased concentrations of WGA also stabilized discoid shape in pronase-digested cells containing no detectable intact glycophorin. In contrast, cell digestion with sialidase abolished the shape-stabilizing effect of WGA. The results suggest that the membrane skeleton is not involved in WGA shape stabilization. Rather, they suggest that glycoproteins and glycolipids interact with the lectin to stabilize cell surface molecular associations, forming a superficial calyx that inhibits outward, but not inward, membrane bending.

Transfer of membrane proteins from human platelets to liposomal fraction by interaction with liposomes containing an artificial boundary lipid

The direct transfer of membrane proteins from human platelets to the liposomal fraction was examined, particularly in relation to platelet activation during the process. The incorporation of an artificial boundary lipid, 1,2-dimyristoylamido-1,2-deoxyphosphatidylcholine (DDPC), in the interacting liposome considerably enhanced the efficiency of the protein transfer. The transfer proceeded with neither significant activation nor lysis of the platelet, and the activation of the platelet with thrombin did not affect the amount of the transferred proteins. A wide range of platelet membrane proteins was transferred, and they were almost comparable to those in a sample prepared by glycerol lysis/centrifugation. In addition, they included the major surface glycoproteins GPIIb and GPIIIa without noticeable contamination of soluble cytosol proteins. The protein transfer method is a one-pot process and clearly more convenient than the conventional 'extract and reconstitute' approach. These results strongly support the use of the transfer process, especially with DDPC, as an alternative to the conventional detergent-solubilization or the solvent-extraction methods for preparation of samples of platelet membrane proteins.

Cytochrome b5 and a recombinant protein containing the cytochrome b5 hydrophobic domain spontaneously associate with the plasma membranes of cells

Both cytochrome b5, isolated from rabbit liver microsomes, and LacZ:HP, a recombinant protein consisting of enzymatically active Escherichia coli beta-galactosidase coupled to the C-terminal membrane-anchoring hydrophobic domain of cytochrome b5, were shown to spontaneously associate with the plasma membranes of erythrocytes and 3T3 cells. Association was promoted by low pH values, but proceeded satisfactorily over several hours at physiological pH and temperature. About 150,000 cytochrome b5 molecules or 100,000 LacZ:HP molecules could be associated per erythrocyte. These proteins were not removed from the membrane by extensive washing, even at high ionic strength. After incubation with fluorescently labeled cytochrome b5 or LacZ:HP, cells displayed fluorescent membranes. The lateral mobility of fluorescently labeled cytochrome b5 and LacZ:HP was measured by photo-bleaching techniques. In the plasma membrane of erythrocytes and 3T3 cells, the apparent lateral diffusion coefficient D ranged from 1.0.10(-9) to 8.10(-9) cm2 s-1 with a mobile fraction M between 0.4 and 0.6. The lateral mobility of these proteins closely resembled that reported for lipid-anchored proteins and was much higher than that reported for Band 3, an erythrocyte membrane-spanning protein with a large cytoplasmic domain. These results suggest that the hydrophobic domain of cytochrome b5 could be employed as a universal, laterally mobile membrane anchor to associate a variety of diagnostically and therapeutically useful recombinant proteins with cells.

Induction of in vitro and in vivo anti-tumor responses by sensitization of mice with liposomes containing a crude butanol extract of leukemia cells and transferred inter-membranously with cell-surface proteins

Generation of cytotoxic T lymphocytes (CTL) in vitro and tumor-rejection responses by sensitization of semi-syngeneic mice with tumor-antigen-reconstituted liposomes were investigated. Liposomes were prepared from a crude butanol extract (CBE) of BALBRVD leukemia cells and egg phosphatidylcholine (PC): 1,2-dimyristoylamido-1,2-deoxyphosphatidylcholine (DDPC) (3:2) or dimyristoylphosphatidylcholine (DMPC):DDPC (1:4). Inter-membrane protein transfer (IMPT) liposomes were prepared by incubating BALBRVD cells with DMPC:DDPC (1:4) liposomes. Sensitization of male CB6F1 mice with CBE or IMPT liposomes induced a level of cytotoxicity similar to that on sensitization with mitomycin-C(MMC)-treated BALBRVD against BALBRVD target cells after in vitro sensitization with the tumor cells. Sensitization with CBE alone resulted in only marginal cytotoxicity. The cytotoxic effector cells induced by either mode of sensitization were CD8+ T-cells whose recognition was Kd-restricted. No difference in specificity was observed with the different modes of sensitization. Two in vivo immunizations with CBE or with CBE liposomes at a dose of 25 micrograms of protein (equivalent to 2.5 x 10(7) cells) cause moderate inhibition of BALBRVD tumor growth in male CB6F1 mice and immunization with IMPT liposomes at a dose of 1 microgram of protein result in efficient protection.

Kinetics of virus-induced hemolysis measured for single erythrocytes

Individual erythrocytes are visible in bright-field microscopy because their enclosed hemoglobin provides a high degree of contrast against a glass slide. Lysis of these cells is detected as the loss of contrast of individual cells caused by the leakage of cell contents. Using these optical properties of erythrocytes, we have developed a new technique to examine the time course of hemolysis induced by Sendai virus at neutral pH and by influenza virus at acidic pH. Viruses were allowed to aggregate erythrocytes at 4 degrees and the temperature was raised to allow hemolysis. Influenza-induced hemolysis at low pH, as determined by this method, occurred at a faster rate than that induced by Sendai at neutral pH. As the lysis of individual cells is detected by this method, we have discerned a cooperative "cluster" effect: Once an erythrocyte within an aggregate lyses, the likelihood of lysis of another erythrocyte in that aggregate is increased.

Vesicle-to-cell protein transfer: insertion of band 3, the erythrocyte anion transporter, into lymphoid cells

Band 3, the erythrocyte anion transporter, transfers spontaneously between human red cells and model membranes. During incubation of intact erythrocytes with sonicated dimyristoylphosphatidylcholine vesicles, the transporter inserts in functional form and native orientation into the liposome bilayer, with the cytoplasmic segment of the protein contacting the lumen of the vesicle [Newton, A. C., Cook, S. L., & Huestis, W. H. (1983) Biochemistry 22, 6110-6117; Huestis, W. H., & Newton, A. C. (1986) J. Biol. Chem. 261, 16274-16278]. When band 3-vesicle complexes are incubated with erythrocytes whose native band 3 has been inhibited irreversibly, reverse transfer of the protein restores anion transport capacity to the cells [Newton, A. C., Cook, S. L., & Huestis, W. H. (1983) Biochemistry 22, 6110-6117]. Here we report the vesicle-mediated transfer of band 3 to human peripheral blood lymphocytes and to cultured murine lymphoma cells (BL/VL3). Subsequent to incubation with protein-vesicle complexes, both lymphoid cell types exhibit a 2-4-fold increase in the rate of chloride uptake. This enhanced permeability is inhibited greater than or equal to 98% by the exofacial band 3 inhibitor 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid, consistent with right-side-out insertion of functional band 3 into the lymphoid cell membrane.

Lymphoma-vesicle interactions: vesicle adsorption, membrane fragmentation, and intermembrane protein transfer

Sonicated dimyristoylphosphatidylcholine vesicles interact with cultured murine lymphoma (BL/VL3) to generate complexes of vesicle and cell membrane components. Cell-free supernatants harvested after cell-vesicle incubations contain three distinct lipid species that can be separated by density gradient centrifugation. Analysis of protein and lipid composition and assays for cell and vesicle lumen contents reveal that the densest of the three lipid species comprises sealed plasma membrane fragments complexed with vesicles, while the least dense species is indistinguishable from pure phospholipid vesicles. The third, intermediate density species consists of topologically intact vesicles with associated plasma membrane proteins but without detectable cell lipids or cytoplasmic components. The membrane fragmentation and cell-to-vesicle protein transfer observed during lymphoma-vesicle incubations are examined as functions of cell and vesicle concentrations and incubation time.