scholarly journals Identification of an Outer Segment Targeting Signal in the Cooh Terminus of Rhodopsin Using Transgenic Xenopus laevis

2000 ◽  
Vol 151 (7) ◽  
pp. 1369-1380 ◽  
Author(s):  
Beatrice M. Tam ◽  
Orson L. Moritz ◽  
Lawrence B. Hurd ◽  
David S. Papermaster
Keyword(s):  
Amino Acids ◽  
Xenopus Laevis ◽  
Fusion Proteins ◽  
Outer Segment ◽  
Fluorescent Protein ◽  
Localization Signal ◽  
Targeting Signal ◽  
Retinal Degenerative Diseases ◽  
Membrane Spanning ◽  
Green Fluorescent

Mislocalization of the photopigment rhodopsin may be involved in the pathology of certain inherited retinal degenerative diseases. Here, we have elucidated rhodopsin's targeting signal which is responsible for its polarized distribution to the rod outer segment (ROS). Various green fluorescent protein (GFP)/rhodopsin COOH-terminal fusion proteins were expressed specifically in the major red rod photoreceptors of transgenic Xenopus laevis under the control of the Xenopus opsin promoter. The fusion proteins were targeted to membranes via lipid modifications (palmitoylation and myristoylation) as opposed to membrane spanning domains. Membrane association was found to be necessary but not sufficient for efficient ROS localization. A GFP fusion protein containing only the cytoplasmic COOH-terminal 44 amino acids of Xenopus rhodopsin localized exclusively to ROS membranes. Chimeras between rhodopsin and α adrenergic receptor COOH-terminal sequences further refined rhodopsin's ROS localization signal to its distal eight amino acids. Mutations/deletions of this region resulted in partial delocalization of the fusion proteins to rod inner segment (RIS) membranes. The targeting and transport of endogenous wild-type rhodopsin was unaffected by the presence of mislocalized GFP fusion proteins.

scholarly journals The C Terminus of Peripherin/rds Participates in Rod Outer Segment Targeting and Alignment of Disk Incisures

2004 ◽  
Vol 15 (4) ◽  
pp. 2027-2037 ◽  
Author(s):  
Beatrice M. Tam ◽  
Orson L. Moritz ◽  
David S. Papermaster
Keyword(s):  
Fusion Proteins ◽  
Outer Segment ◽  
Protein Targeting ◽  
Fluorescent Protein ◽  
Membrane Domains ◽  
Rod Outer Segment ◽  
Retinal Degenerations ◽  
C Terminus ◽  
Green Fluorescent

Protein targeting is essential for domain specialization in polarized cells. In photoreceptors, three distinct membrane domains exist in the outer segment: plasma membrane, disk lamella, and disk rim. Peripherin/retinal degeneration slow (rds) and rom-1 are photoreceptor-specific members of the transmembrane 4 superfamily of transmembrane proteins, which participate in disk morphogenesis and localize to rod outer segment (ROS) disk rims. We examined the role of their C termini in targeting by generating transgenic Xenopus laevis expressing green fluorescent protein (GFP) fusion proteins. A GFP fusion containing residues 317-336 of peripherin/rds localized uniformly to disk membranes. A longer fusion (residues 307-346) also localized to the ROS but exhibited higher affinity for disk rims than disk lamella. In contrast, the rom-1 C terminus did not promote ROS localization. The GFP-peripherin/rds fusion proteins did not immunoprecipitate with peripherin/rds or rom-1, suggesting this region does not form intermolecular interactions and is not involved in subunit assembly. Presence of GFP-peripherin/rds fusions correlated with disrupted incisures, disordered ROS tips, and membrane whorls. These abnormalities may reflect competition of the fusion proteins for other proteins that interact with peripherin/rds. This work describes novel roles for the C terminus of peripherin/rds in targeting and maintaining ROS structure and its potential involvement in inherited retinal degenerations.

scholarly journals The sorting sequence of the peroxisomal integral membrane protein PMP47 is contained within a short hydrophilic loop.

1996 ◽  
Vol 133 (2) ◽  
pp. 269-280 ◽  
Author(s):  
J M Dyer ◽  
J A McNew ◽  
J M Goodman
Keyword(s):  
Amino Acids ◽  
Fluorescent Protein ◽  
Membrane Surface ◽  
Integral Membrane Protein ◽  
The Matrix ◽  
Peroxisomal Targeting ◽  
Targeting Signal ◽  
Green Fluorescent ◽  
Necessary And Sufficient ◽  
Hydrophilic Loop

No targeting sequence for peroxisomal integral membrane proteins has yet been identified. We have previously shown that a region of 67 amino acids is necessary to target Pmp47, a protein that spans the membrane six times, to peroxisomes. This region comprises two membrane spans and the intervening loop. We now demonstrate that the 20 amino acid loop, which is predicted to face the matrix, is both necessary and sufficient for peroxisomal targeting. Sufficiency was demonstrated with both chloramphenicol acetyltransferase and green fluorescent protein as carriers. There is a cluster of basic amino acids in the middle of the loop that we predict protrudes from the membrane surface into the matrix by a flanking stem structure. We show that the targeting signal is composed of this basic cluster and a block of amino acids immediately down-stream from it.

scholarly journals Rtn1p Is Involved in Structuring the Cortical Endoplasmic Reticulum

2006 ◽  
Vol 17 (7) ◽  
pp. 3009-3020 ◽  
Author(s):  
Johan-Owen De Craene ◽  
Jeff Coleman ◽  
Paula Estrada de Martin ◽  
Marc Pypaert ◽  
Scott Anderson ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Fluorescent Protein ◽  
Cell Cortex ◽  
Proteomic Screen ◽  
Wide Range ◽  
Membrane Spanning ◽  
Green Fluorescent ◽  
Hydrophilic Loop ◽  
Yeast Mutants

The endoplasmic reticulum (ER) contains both cisternal and reticular elements in one contiguous structure. We identified rtn1Δ in a systematic screen for yeast mutants with altered ER morphology. The ER in rtn1Δ cells is predominantly cisternal rather than reticular, yet the net surface area of ER is not significantly changed. Rtn1-green fluorescent protein (GFP) associates with the reticular ER at the cell cortex and with the tubules that connect the cortical ER to the nuclear envelope, but not with the nuclear envelope itself. Rtn1p overexpression also results in an altered ER structure. Rtn proteins are found on the ER in a wide range of eukaryotes and are defined by two membrane-spanning domains flanking a conserved hydrophilic loop. Our results suggest that Rtn proteins may direct the formation of reticulated ER. We independently identified Rtn1p in a proteomic screen for proteins associated with the exocyst vesicle tethering complex. The conserved hydophilic loop of Rtn1p binds to the exocyst subunit Sec6p. Overexpression of this loop results in a modest accumulation of secretory vesicles, suggesting impaired exocyst function. The interaction of Rtn1p with the exocyst at the bud tip may trigger the formation of a cortical ER network in yeast buds.

scholarly journals Cellular Targets of Functional and Dysfunctional Mutants of Tobacco Mosaic Virus Movement Protein Fused to Green Fluorescent Protein

2000 ◽  
Vol 74 (23) ◽  
pp. 11339-11346 ◽  
Author(s):  
Vitaly Boyko ◽  
Jessica van der Laak ◽  
Jacqueline Ferralli ◽  
Elena Suslova ◽  
Myoung-Ok Kwon ◽  
...  
Keyword(s):  
Amino Acids ◽  
Green Fluorescent Protein ◽  
Tobacco Mosaic Virus ◽  
Inclusion Bodies ◽  
Fluorescent Protein ◽  
Movement Protein ◽  
Leading Edge ◽  
Intercellular Transport ◽  
C Terminus ◽  
Green Fluorescent

ABSTRACT Intercellular transport of tobacco mosaic virus (TMV) RNA involves the accumulation of virus-encoded movement protein (MP) in plasmodesmata (Pd), in endoplasmic reticulum (ER)-derived inclusion bodies, and on microtubules. The functional significance of these interactions in viral RNA (vRNA) movement was tested in planta and in protoplasts with TMV derivatives expressing N- and C-terminal deletion mutants of MP fused to the green fluorescent protein. Deletion of 55 amino acids from the C terminus of MP did not interfere with the vRNA transport function of MP:GFP but abolished its accumulation in inclusion bodies, indicating that accumulation of MP at these ER-derived sites is not a requirement for function in vRNA intercellular movement. Deletion of 66 amino acids from the C terminus of MP inactivated the protein, and viral infection occurred only upon complementation in plants transgenic for MP. The functional deficiency of the mutant protein correlated with its inability to associate with microtubules and, independently, with its absence from Pd at the leading edge of infection. Inactivation of MP by N-terminal deletions was correlated with the inability of the protein to target Pd throughout the infection site, whereas its associations with microtubules and inclusion bodies were unaffected. The observations support a role of MP-interacting microtubules in TMV RNA movement and indicate that MP targets microtubules and Pd by independent mechanisms. Moreover, accumulation of MP in Pd late in infection is insufficient to support viral movement, confirming that intercellular transport of vRNA relies on the presence of MP in Pd at the leading edge of infection.

scholarly journals EXPRESSION OF THE GREEN FLUORESCENT PROTEIN DERIVATIVE S65T IN XENOPUS LAEVIS OOCYTES

1996 ◽  
Vol 17 (3) ◽  
pp. 221-225 ◽  
Author(s):  
JULIE M. MATHESON ◽  
ATSUSHI MIYAWAKI ◽  
AKIRA MUTO ◽  
TAKAFUMI INOUE ◽  
KATSUHIKO MIKOSHIBA
Keyword(s):  
Green Fluorescent Protein ◽  
Xenopus Laevis ◽  
Fluorescent Protein ◽  
Green Fluorescent

scholarly journals Bifunctional fusion proteins containing the sequence of the bradykinin homologue maximakinin: activities at the rat bradykinin B2 receptor

2018 ◽  
Vol 96 (5) ◽  
pp. 459-470 ◽  
Author(s):  
Xavier Charest-Morin ◽  
Robert Lodge ◽  
François Marceau
Keyword(s):  
Fusion Proteins ◽  
Enhanced Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Protein Denaturation ◽  
Epifluorescence Microscopy ◽  
Terminal Sequence ◽  
Protein Ligands ◽  
C Terminus ◽  
Bona Fide ◽  
Green Fluorescent

To support bradykinin (BK) B2 receptor (B2R) detection and therapeutic stimulation, we developed and characterized fusion proteins consisting of the BK homolog maximakinin (MK), or variants, positioned at the C-terminus of functional proteins (enhanced green fluorescent protein (EGFP), the peroxidase APEX2, or human serum albumin (HSA)). EGFP-MK loses its reactivity with anti-BK antibodies and molecular mass as it progresses in the endosomal tract of cells expressing rat B2Rs (immunoblots, epifluorescence microscopy). APEX2-(NG)15-MK is a bona fide agonist of the rat, but not of the human B2R (calcium and c-Fos signaling) and is compatible with the cytochemistry reagent TrueBlue (microscopy), a luminol-based reagent, or 3,3′,5,5′-tetramethylbenzidine (luminescence or colourimetric B2R detection, cell well plate format). APEX2-(NG)15-MK is a non-isotopic ligand suitable for drug discovery via binding competition. Affinity-purified secreted forms of HSA fused with peptides possessing the C-terminal MK or BK sequence failed to stimulate the rat B2R in the concentration range of 50–600 nmol/L. However, the non-secreted construction myc-HSA-MK is a B2R agonist, indicating that protein denaturation made the C-terminal sequence available for receptor binding. Fusion protein ligands of the B2R are stable but subjected to slow intracellular inactivation, strong species specificity, and possible steric hindrance between the receptor and large proteins.

scholarly journals The sustainability of interactions between the orexin-1 receptor and β-arrestin-2 is defined by a single C-terminal cluster of hydroxy amino acids and modulates the kinetics of ERK MAPK regulation

2005 ◽  
Vol 387 (3) ◽  
pp. 573-584 ◽  
Author(s):  
Sandra MILASTA ◽  
Nicholas A. EVANS ◽  
Laura ORMISTON ◽  
Shelagh WILSON ◽  
Robert J. LEFKOWITZ ◽  
...  
Keyword(s):  
Amino Acids ◽  
Fluorescent Protein ◽  
Weak Interactions ◽  
Dependent Manner ◽  
Wild Type ◽  
Erk Mapk ◽  
Hydroxy Amino ◽  
C Terminus ◽  
Green Fluorescent ◽  
Kinetics Of

The orexin-1 receptor interacts with β-arrestin-2 in an agonist-dependent manner. In HEK-293T cells, these two proteins became co-internalized into acidic endosomes. Truncations from the C-terminal tail did not prevent agonist-induced internalization of the orexin-1 receptor or alter the pathway of internalization, although such mutants failed to interact with β-arrestin-2 in a sustained manner or produce its co-internalization. Mutation of a cluster of three threonine and one serine residue at the extreme C-terminus of the receptor greatly reduced interaction and abolished co-internalization of β-arrestin-2–GFP (green fluorescent protein). Despite the weak interactions of this C-terminally mutated form of the receptor with β-arrestin-2, studies in wild-type and β-arrestin-deficient mouse embryo fibroblasts confirmed that agonist-induced internalization of this mutant required expression of a β-arrestin. Although without effect on agonist-mediated elevation of intracellular Ca2+ levels, the C-terminally mutated form of the orexin-1 receptor was unable to sustain phosphorylation of the MAPKs (mitogen-activated protein kinases) ERK1 and ERK2 (extracellular-signal-regulated kinases 1 and 2) to the same extent as the wild-type receptor. These studies indicate that a single cluster of hydroxy amino acids within the C-terminal seven amino acids of the orexin-1 receptor determine the sustainability of interaction with β-arrestin-2, and indicate an important role of β-arrestin scaffolding in defining the kinetics of orexin-1 receptor-mediated ERK MAPK activation.

scholarly journals The First 35 Amino Acids and Fatty Acylation Sites Determine the Molecular Targeting of Endothelial Nitric Oxide Synthase into the Golgi Region of Cells: A Green Fluorescent Protein Study

1997 ◽  
Vol 137 (7) ◽  
pp. 1525-1535 ◽  
Author(s):  
Jianwei Liu ◽  
Thomas E. Hughes ◽  
William C. Sessa
Keyword(s):  
Nitric Oxide ◽  
Amino Acids ◽  
Fluorescent Protein ◽  
3T3 Cells ◽  
Fatty Acylation ◽  
Golgi Region ◽  
Green Fluorescent ◽  
Oxide Synthase ◽  
Nih 3T3 ◽  
Endothelial Nitric Oxide

Catalytically active endothelial nitric oxide synthase (eNOS) is located on the Golgi complex and in the caveolae of endothelial cells (EC). Mislocalization of eNOS caused by mutation of the N-myristoylation or cysteine palmitoylation sites impairs production of stimulated nitric oxide (NO), suggesting that intracellular targeting is critical for optimal NO production. To investigate the molecular determinants of eNOS targeting in EC, we constructed eNOS–green fluorescent protein (GFP) chimeras to study its localization in living and fixed cells. The full-length eNOS–GFP fusion colocalized with a Golgi marker, mannosidase II, and retained catalytic activity compared to wild-type (WT) eNOS, suggesting that the GFP tag does not interfere with eNOS localization or function. Experiments with different size amino-terminal fusion partners coupled to GFP demonstrated that the first 35 amino acids of eNOS are sufficient to target GFP into the Golgi region of NIH 3T3 cells. Additionally, the unique (Gly-Leu)5 repeat located between the palmitoylation sites (Cys-15 and -26) of eNOS is necessary for its palmitoylation and thus localization, but not for N-myristoylation, membrane association, and NOS activity. The palmitoylation-deficient mutants displayed a more diffuse fluorescence pattern than did WT eNOS–GFP, but still were associated with intracellular membranes. Biochemical studies also showed that the palmitoylation-deficient mutants are associated with membranes as tightly as WT eNOS. Mutation of the N-myristoylation site Gly-2 (abolishing both N-myristoylation and palmitoylation) caused the GFP fusion protein to distribute throughout the cell as GFP alone, consistent with its primarily cytosolic nature in biochemical studies. Therefore, eNOS targets into the Golgi region of NIH 3T3 cells via the first 35 amino acids, including N-myristoylation and palmitoylation sites, and its overall membrane association requires N-myristoylation but not cysteine palmitoylation. These results suggest a novel role for fatty acylation in the specific compartmentalization of eNOS and most likely, for other dually acylated proteins, to the Golgi complex.

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