Light-induced Reorganization of Phospholipids in Rod Disc Membranes

Hessel, Elke; Müller, Peter; Herrmann, Andreas; Hofmann, Klaus Peter

doi:10.1074/jbc.m009061200

Cited by 55 publications

(56 citation statements)

References 48 publications

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“…For example, PS, which undergoes a light-dependent translocation to the cytoplasmic side of the membrane (39), may interact specifically with arrestin in the native ROS as it appears to do with transducin (54). Intriguingly phosphoinositide has been implicated in the trafficking of Drosophila visual arrestin and recruitment of ␤-arrestin to clathrin-coated pits, although…”

Section: Discussionmentioning

confidence: 99%

“…Rho is certainly intimately associated with its surrounding phospholipids: it immobilizes ϳ25 phospholipids and induces a reorganization of these lipids upon light activation (39,40). In fact, Rho and ROS phospholipids interact so tightly that it is very difficult to remove all lipids during Rho purification with detergents or even with organic solvents (20 -22).…”

Section: Discussionmentioning

confidence: 99%

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Dynamics of Arrestin-Rhodopsin Interactions

Sommer

Smith

Farrens

2006

Journal of Biological Chemistry

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We report that acidic phospholipids can restore the binding of visual arrestin to purified rhodopsin solubilized in n-dodecyl-␤-Dmaltopyranoside. We used this finding to investigate the interplay between arrestin binding and the status of the retinal chromophore ligand in the receptor binding pocket. Our results showed that arrestin can interact with the late photoproduct Meta III and convert it to a Meta II-like species. Interestingly in these mixed micelles, the release of retinal and arrestin was no longer directly coupled as it is in the native rod disk membrane. For example, up to ϳ50% of the retinal could be released even though arrestin remains bound to the receptor in a long lived complex. We anticipate that this new ability to study these proteins in a defined, purified system will facilitate further structural and dynamic studies of arrestinrhodopsin interactions.The integral membrane protein rhodopsin (Rho) 2 enables the conversion of light to nerve signals in the rod cells, resulting in dim light vision (1-3). In the dark, the chromophore (11-cis-retinal) is linked to Rho at Lys 296 by a protonated Schiff base ( max ϳ 500 nm). Light absorption isomerizes the chromophore to all-trans-retinal. Within milliseconds two photoproducts evolve, Meta I ( max ϳ 480 nm) and Meta II ( max ϳ 380 nm), which are in a pH-and temperature-sensitive equilibrium.The ability of Meta II to bind and activate the G-protein transducin (4) is terminated in several ways. Meta II can decay through hydrolysis of the Schiff base linkage and release of retinal, a process that takes ϳ1 min at physiological temperature and pH (5). Alternatively Meta II can decay to the long lived retinal storage photoproduct Meta III ( max ϳ 470 nm) in which the Schiff base is intact and protonated (6 -9). Finally Rho signaling can be blocked through a series of protein-protein interactions that involves phosphorylation of the C-terminal tail of Rho by Rho kinase and binding of the protein arrestin (10).Earlier we found that these inactivation mechanisms are related. That is, arrestin release and retinal release appear to be directly linked events: both are described by similar activation energies, and arrestin slows the rate of retinal release ϳ2-fold at physiological temperatures. Intriguingly we also found that a fraction of the arrestin remains bound to ROS*-P long after "active" Meta II decay (5).In the present work, we expanded upon these studies and made several surprising discoveries. First, we found that adding phospholipids restores arrestin binding to purified Rho*-P solubilized in n-dodecyl-␤-D-maltopyranoside (DM). Second, we clearly established in the mixed micelle system that arrestin interacts with the post-Meta II photodecay product Meta III. Finally we found that arrestin and retinal release appear to be unlinked in mixed micelles with the acidic phospholipids PS, PI, and PA showing a more pronounced effect than the neutral phospholipids PC and PE ( Fig. 1 shows a scheme of the different lipid head groups). Intriguingly with the ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Dynamics of Arrestin-Rhodopsin Interactions

Sommer

Smith

Farrens

2006

Journal of Biological Chemistry

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“…Although ROS membranes contain only ϳ15 mol % PS, the distribution of PS appears to be asymmetric across the bilayer in dark-adapted discs (43). Hence, we assumed in our calculations that all of the PS is located on the outer leaflet of ROS membranes and that 2:1 PC/PS is a reasonable approximation for the lipid composition to which G t ␤␥ binds under physiological conditions.…”

Section: Electrostatic Interaction Of G T ␤␥ With Phospholipid Membranesmentioning

confidence: 99%

The Role of Electrostatic Interactions in the Regulation of the Membrane Association of G Protein βγ Heterodimers

Murray¹,

McLaughlin²,

Honig³

2001

Journal of Biological Chemistry

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In this paper we report calculations of electrostatic interactions between the transducin (G t ) ␤␥ heterodimer (G t ␤␥) and phospholipid membranes. Although membrane association of G t ␤␥ is due primarily to the hydrophobic penetration into the membrane interior of a farnesyl chain attached to the ␥ subunit, structural studies have revealed that there is a prominent patch of basic residues on the surface of the ␤ subunit surrounding the site of farnesylation that is exposed upon dissociation from the G t ␣ subunit. Moreover, phosducin, which produces dissociation of G t ␤␥ from membranes, interacts directly with G t ␤␥ and introduces a cluster of acidic residues into this region. The calculations, which are based on the finite difference Poisson-Boltzmann method, account for a number of experimental observations and suggest that charged residues play a role in mediating protein-membrane interactions. Specifically, the calculations predict the following. 1) Favorable electrostatic interactions enhance the membrane partitioning due to the farnesyl group by an order of magnitude although G t ␤␥ has a large net negative charge (؊12). 2) This electrostatic attraction positions G t ␤␥ so that residues implicated in mediating the interaction of G t ␤␥ with its membrane-bound effectors are close to the membrane surface.3) The binding of phosducin to G t ␤␥ diminishes the membrane partitioning of G t ␤␥ by an order of magnitude. 4) Lowering the ionic strength of the solution converts the electrostatic attraction into a repulsion. Sequence analysis and homology model building suggest that our conclusions may be generalized to other G␤␥ and phosducin isoforms as well.The interaction of proteins with cellular membranes is a central feature of signal transduction. Many proteins involved in interfacial signaling contain a lipophilic modification (e.g. myristate and farnesyl) that contributes to membrane association by partitioning hydrophobically into the membrane interior (1, 2). Examples of such proteins include heterotrimeric G proteins, small GTPases, and nonreceptor tyrosine kinases. A lipid modification alone usually cannot provide enough energy to keep a protein anchored to a cellular membrane (3) and often occurs in conjunction with additional membrane binding motifs. For example, most Src family kinases (1), H-and N-Ras (4), and many G␣ subunits (5) have dual lipophilic modifications, while other proteins, e.g. K-Ras4B (6, 7) and Src itself (8, 9), have both a lipophilic attachment and an adjacent cluster of basic residues that are attracted electrostatically to the charged surface of lipid bilayers. Heterotrimeric G proteins are acylated on the ␣ subunit and prenylated on the ␥ subunit, and the membrane association of the inactive heterotrimer is due primarily to the penetration of both of these lipophilic modifications into the hydrocarbon region of the membrane (10). The exchange of GTP for GDP on the ␣ subunit, catalyzed by an activated G protein-coupled receptor, results in the dissociation of G␣ from the G␤␥ h...

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“…Lipids that undergo slow exchange between the protein and the bulk bilayer may directly influence the light response of rhodopsin. For example, in the disk membrane it has been shown that the phospholipids exhibit a reorganization in response to light [109]. The effect of cholesterol on rhodopsin activity can be largely explained by its ability to alter bulk membrane properties.…”

Section: Organization Of Cholesterol In Disk Membranesmentioning

confidence: 99%

The role of cholesterol in rod outer segment membranes

Albert

Boesze‐Battaglia

2005

Progress in Lipid Research

112

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The photoreceptor rod outer segment (ROS) provides a unique system in which to investigate the role of cholesterol, an essential membrane constituent of most animal cells. The ROS is responsible for the initial events of vision at low light levels. It consists of a stack of disk membranes surrounded by the plasma membrane. Light capture occurs in the outer segment disk membranes that contain the photopigment, rhodopsin. These membranes originate from evaginations of the plasma membrane at the base of the outer segment. The new disks separate from the plasma membrane and progressively move up the length of the ROS over the course of several days. Thus the role of cholesterol can be evlauated in two distinct membranes. Furthermore, because the disk membranes vary in age it can also be investigated in a membrane as a function of the membrane age. The plasma membrane is enriched in cholesterol and in saturated fatty acids species relative to the disk membrane. The newly formed disk membranes have 6-fold more cholesterol than disks at the apical tip of the ROS. The partitioning of cholesterol out of disk membranes as they age and are apically displaced is consistent with the high PE content of disk membranes relative to the plasma membrane. The cholesterol composition of membranes has profound consequences on the major protein, rhodopsin. Biophysical studies in both model membranes and in native membranes have demonstrated that cholesterol can modulate the activity of rhodopsin by altering the membrane hydrocarbon environment. These studies suggest that mature disk membranes initiate the visual signal cascade more effectively than the newly synthesized, high cholesterol basal disks. Although rhodopsin is also the major protein of the plasma membrane, the high membrane cholesterol content inhibits rhodopsin participation in the visual transduction cascade. In addition to its effect on the hydrocarbon region, cholesterol may interact directly with rhodopsin. While high cholesterol inhibits rhodopsin activation, it also stabilizes the protein to denaturation. Therefore the disk membrane must perform a balancing act providing sufficient cholestrol to confer stability but without making the membrane too restrictive to receptor activation. Within a given disk membrane, it is likely that cholesterol exhibits an asymmetric distribution between the inner and outer bilayer leaflets. Furthremore, there is some evidence of cholesterol microdomains in the disk membranes. The availability of the disk protein, rom-1 may be sensitive to membrane cholesterol. The effects exerted by cholesterol on rhodopsin function have far-reaching implications for the study of G-protein coupled receptors as a whole. These studies show that the function of a membrane receptor can be modulated by modification of HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript the lipid bilayer, particularly cholesterol. This provides a powerful means of fine-tuning the activity of a membrane protein without resorting ...

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Light-induced Reorganization of Phospholipids in Rod Disc Membranes

Cited by 55 publications

References 48 publications

Dynamics of Arrestin-Rhodopsin Interactions

Dynamics of Arrestin-Rhodopsin Interactions

The Role of Electrostatic Interactions in the Regulation of the Membrane Association of G Protein βγ Heterodimers

The role of cholesterol in rod outer segment membranes

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