Rick H. Cote

Rick H. Cote
University of New Hampshire | UNH · Department of Molecular, Celluar and Biomedical Sciences

Ph.D.

About

75
Publications
15,813
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Introduction
My laboratory studies the molecular mechanisms of visual signaling in rod and cone photoreceptors, with an emphasis on the structure, function, and regulation of the photoreceptor cyclic nucleotide phosphodiesterase (PDE6).
Additional affiliations
August 1995 - July 1996
University of Washington Seattle
Position
  • Subcloning, expression and purification of phosphodiesterase subunits.
Description
  • Sabbatical research
March 1988 - present
University of New Hampshire
Position
  • Role of cGMP in photoreceptor function
June 1986 - July 1986
Woods Hole Marine Biological Laboratory
Position
  • Characterization of guanylate cyclase in invertebrate photoreceptors
Description
  • Postdoctoral research
Education
August 1974 - December 1980
University of Wisconsin–Madison
Field of study
  • Molecular Biology
August 1970 - June 1974
Tufts University
Field of study
  • Biology-Chemistry

Publications

Publications (75)
Article
G-protein coupled signaling pathways are organized into multi-protein complexes called signalosomes that are located within and on cellular membranes. We describe the use of silica nanoparticles coated with a unilamellar phospholipid bilayer (lipobeads) to reconstitute the activated photoreceptor G-protein α-subunit (Gtα*) with its cognate effector...
Article
Full-text available
Rod and cone photoreceptors of the vertebrate retina utilize cGMP as the primary intracellular messenger for the visual signaling pathway that converts a light stimulus into an electrical response. cGMP metabolism in the signal-transducing photoreceptor outer segment reflects the balance of cGMP synthesis (catalyzed by guanylyl cyclase) and degrada...
Article
The photoreceptor phosphodiesterase (PDE6) is a member of large family of Class I phosphodiesterases responsible for hydrolyzing the second messengers cAMP and cGMP. PDE6 consists of two catalytic subunits and two inhibitory subunits that form a tetrameric protein. PDE6 is a peripheral membrane protein that is localized to the signal-transducing co...
Article
Regulation of photoreceptor phosphodiesterase (PDE6) activity is responsible for the speed, sensitivity, and recovery of the photoresponse during visual signaling in vertebrate photoreceptor cells. It is hypothesized that physiological differences in the light responsiveness of rods and cones may result in part from differences in the structure and...
Article
Full-text available
Photoreceptor phosphodiesterase 6 (PDE6) is the central effector of the visual excitation pathway in both rod and cone photoreceptors, and PDE6 mutations that alter PDE6 structure or regulation can result in several human retinal diseases. The rod PDE6 holoenzyme consists of two catalytic subunits (Pαβ) whose activity is suppressed in the dark by b...
Article
Photoreceptor phosphodiesterase (PDE6) is the central effector enzyme in the visual excitation pathway in rod and cone photoreceptors. Its tight regulation is essential for the speed, sensitivity, recovery, and adaptation of visual signaling. The rod PDE6 holoenzyme (Pαβγ2) is composed of a catalytic heterodimer (Pαβ) that binds two inhibitory γ su...
Article
Full-text available
Phosphodiesterase-6 (PDE6) plays a central role in both rod and cone phototransduction pathways. In the dark, PDE6 activity is suppressed by its inhibitory γ-subunit (Pγ). Rhodopsin-catalyzed activation of the G protein transducin relieves this inhibition and enhances PDE6 catalysis. We hypothesized that amino acid sequence differences between rod-...
Article
Full-text available
Novel chemical controls are needed that selectively target human, animal, and plant parasitic nematodes with reduced adverse effects on the host or the environment. We hypothesize that the phosphodiesterase (PDE) enzyme family represents a potential target for development of novel nematicides and anthelmintics. To test this, we identified six PDE f...
Article
Meloidogyne spp. (root-knot nematodes) are the most damaging plant-parasitic nematodes to commercial agriculture. Currently used nematicides are of limited effectiveness as well as toxic to other organisms. The present study examines whether disruption of cyclic nucleotide signaling pathways using phosphodiesterase (PDE) inhibitors could serve as t...
Article
Full-text available
The eleven families of the Class I cyclic nucleotide phosphodiesterases (PDEs) are critical for regulation of cyclic nucleotide signaling. PDE5 (important in regulating vascular smooth muscle contraction) and PDE6 (responsible for regulating visual transduction in vertebrate photoreceptors) are structurally similar but have several functional diffe...
Article
Full-text available
Background: The PDE6 γ-subunit serves multiple functions during visual transduction. Results: Several regions of Pγ that interact with PDE6 or transducin were identified. Conclusion: Multiple interacting sites of Pγ with PDE catalytic dimer, transducin, and the transducin/RGS9 complex coordinate the activation and deactivation of PDE6. Significance...
Article
Full-text available
As the central effector of visual transduction, the regulation of photoreceptor phosphodiesterase (PDE6) is controlled by both allosteric mechanisms and extrinsic binding partners. However, the conformational changes and interactions of PDE6 with known interacting proteins are poorly understood. Using a fluorescence detection system for the analyti...
Article
Full-text available
Network Map States Transitions Functions Protein Classes Sequence Interactions Pathways Domains & Motifs Protein Structure Orthologs Sequence Interactions Pathways Domains & Motifs Protein Structure Orthologs Blast Data.
Article
Full-text available
Network Map States Transitions Functions Protein Classes Sequence Interactions Pathways Domains & Motifs Protein Structure Orthologs Sequence Interactions Pathways Domains & Motifs Protein Structure Orthologs Blast Data.
Chapter
This chapter explains the mechanisms involved in the sequestration of cGMP by PDE6 and also by PDE5. Cyclic GMP is the primary intracellular second messenger for visual transduction, and is present in high concentrations in photoreceptor cells. Light stimulation activates PDE6 more than 100-fold, causing free cytoplasmic cGMP to drop to submicromol...
Article
Full-text available
The central enzyme of the visual transduction cascade, cGMP phosphodiesterase (PDE6), is regulated by its gamma-subunit (Pgamma), whose inhibitory constraint is released upon binding of activated transducin. It is generally believed that the last four or five C-terminal amino acid residues of Pgamma are responsible for blocking catalysis. In this p...
Article
Full-text available
Retinal photoreceptor phosphodiesterase (PDE6) is unique among the phosphodiesterase enzyme family not only for its catalytic heterodimer but also for its regulatory gamma-subunits (Pgamma) whose inhibitory action is released upon binding to the G-protein transducin. It is generally assumed that during visual excitation both catalytic sites are rel...
Chapter
This chapter focuses on the catalytic and regulatory features of the photoreceptor phosphodiesterase 6 (PDE6) that make it suitable as the central effector of the visual transduction pathway. Photoreceptor PDE6 is one of the 11 PDE family members that comprise the class I cyclic nucleotide PDE superfamily. These enzymes regulate the cellular levels...
Article
Full-text available
Photoreceptor cGMP phosphodiesterase (PDE6) is the central enzyme in the visual transduction cascade. The PDE6 catalytic subunit contains a catalytic domain and regulatory GAF domains. Unlike most GAF domain-containing cyclic nucleotide phosphodiesterases, little is known about direct allosteric communication of PDE6. In this study, we demonstrate...
Article
Full-text available
The glutamic acid-rich protein-2 (GARP2) is a splice variant of the beta-subunit of the cGMP-gated ion channel of rod photoreceptors. GARP2 is believed to interact with several membrane-associated phototransduction proteins in rod photoreceptors. In this study, we demonstrated that GARP2 is a high affinity PDE6-binding protein and that PDE6 co-puri...
Article
Full-text available
Phosphodiesterase (PDE) inhibitors are important therapeutic agents, but their effects on photoreceptor PDE (PDE6) and photoreceptor cells are poorly understood. The potency and selectivity of various classes of PDE inhibitors on purified rod and cone PDE6 and on intact rod outer segments (ROS) were characterized. The inhibition constant (K(i)) of...
Article
Full-text available
The visual receptor of rods and cones is a covalent complex of the apoprotein, opsin, and the light-sensitive chromophore, 11-cis-retinal. This pigment must fulfill many functions including photoactivation, spectral tuning, signal transmission, inactivation, and chromophore regeneration. Rod and cone photoreceptors employ distinct families of opsin...
Article
Full-text available
The visual transduction pathway in vertebrate photoreceptors transforms a light stimulus entering the photoreceptor outer segments into an electrical response at the synapses of rod and cone photoreceptor cells. This process is mediated by complex biochemical pathways that precisely regulate cGMP levels, thereby controlling the extent, duration, an...
Article
Full-text available
The mammalian rod photoreceptor phosphodiesterase (PDE6) holoenzyme is isolated in both a membrane-associated and a soluble form. Membrane binding is a consequence of prenylation of PDE6 catalytic subunits, whereas soluble PDE6 is purified with a 17-kDa prenyl-binding protein (PDEdelta) tightly bound. This protein, here termed PrBP/delta, has been...
Article
Full-text available
The photoreceptor phosphodiesterase (PDE6) is the central effector of visual transduction in vertebrate retinal photoreceptors. Distinct isozymes of PDE6 exist in rods and cones. Mam-malian retina serves as an abundant source of tissue for PDE6 purification. Methods are described for the isolation and purification of membrane-associated PDE6 from r...
Article
A 17-kDa prenyl-binding protein, PrBP(PDEdelta), is highly conserved among various species from human to Caenorhabditis elegans. First identified as a putative regulatory delta subunit of the cyclic nucleotide phosphodiesterase (PDE6) purified from mammalian photoreceptor cells, PrBP(PDEdelta) has been hypothesized to reduce activation of PDE6 by t...
Article
Full-text available
Of the 11 families of mammalian cyclic nucleotide phosphodiesterases (PDEs), 5 contain regulatory domains capable of binding cyclic guanosine 5'-monophosphate (cGMP). The best understood of the GAF-containing PDEs is the family of rod (PDE6R) and cone (PDE6C) photo receptor PDEs. Binding of cGMP to the rod PDE6 catalytic dimer (alphabeta) allosteri...
Article
Phosphodiesterase 6 (PDE6) is highly concentrated in the retina. It is most abundant in the internal membranes of retinal photoreceptors, where it reduces cytoplasmic levels of cyclic guanosine monophosphate (cGMP) in rod and cone outer segments in response to light. The rod PDE6 holoenzyme comprises alpha and beta catalytic subunits and two identi...
Chapter
This chapter explains the mechanisms involved in the sequestration of cGMP by PDE6 and also by PDE5. Cyclic GMP is the primary intracellular second messenger for visual transduction, and is present in high concentrations in photoreceptor cells. Light stimulation activates PDE6 more than 100-fold, causing free cytoplasmic cGMP to drop to submicromol...
Chapter
The PDE6 family is one of five families of PDEs that contain noncatalytic, cGMP-binding GAF domains. The catalytic and regulatory features of the PDE6 family make it uniquely suited as the central effector of the visual transduction pathway. The lifetime of activated rod phosphodiesterase 6 (PDE6) during rod phototransduction is a highly regulated...
Article
Full-text available
Phosphorylation of the inhibitory gamma subunit (Pgamma) of rod cGMP phosphodiesterase (PDE6) has been reported to turn off visual excitation without the requirement for inactivation of the photoreceptor G-protein transducin. We evaluated the significance of Pgamma phosphorylation for PDE6 regulation by preparing Pgamma stoichiometrically phosphory...
Article
Phosphodiesterase 6 (PDE6), a multisubunit (alphabetagamma(2)delta) enzyme, plays a major role in visual function by hydrolysing cGMP in response to a light stimulus. Solubilized bovine rod PDE6 molecules depleted of their gamma subunits were purified to homogeneity from bovine retinal rods and their molecular organization was investigated by elect...
Article
Full-text available
The central effector of visual transduction in retinal rod photoreceptors, cGMP phosphodiesterase (PDE6), is a catalytic heterodimer (alphabeta) to which low molecular weight inhibitory gamma subunits bind to form the nonactivated PDE holoenzyme (alphabetagamma(2)). Although it is known that gamma binds tightly to alphabeta, the binding affinity fo...
Article
Full-text available
The rod photoreceptor phosphodiesterase (PDE) is unique among all known vertebrate PDE families for several reasons. It is a catalytic heterodimer (alphabeta); it is directly activated by a G-protein, transducin; and its active sites are regulated by inhibitory gamma subunits. Rod PDE binds cGMP at two noncatalytic sites on the alphabeta dimer, but...
Article
Full-text available
The photoreceptor 3':5'-cyclic nucleotide phosphodiesterase (PDE) is the central enzyme of visual excitation in rod photoreceptors. The hydrolytic activity of PDE is precisely regulated by its inhibitory gamma subunit (Pgamma), which binds directly to the catalytic site. We examined the inhibition of frog rod outer segment PDE by endogenous Pgamma,...
Article
Full-text available
The binding of cGMP to the noncatalytic sites on two isoforms of the phosphodiesterase (PDE) from mammalian rod outer segments has been characterized to evaluate their role in regulating PDE during phototransduction. Nonactivated, membrane-associated PDE (PDE-M, alpha beta gamma2) has one exchangeable site for cGMP binding; endogenous cGMP remains...
Article
Full-text available
The ability of inhibitors selective for the type 5 phosphodiesterase isozyme (PDE5) to act on the photoreceptor PDE isozyme (PDE6, the central effector enzyme for visual transduction) is poorly understood. Because PDE5 inhibitors are currently used as therapeutic agents, it is important to assess the potency and mechanism of action of this class of...
Article
Full-text available
The cGMP-specific phosphodiesterase (PDE) of retinal photoreceptors is a central regulatory enzyme in the visual transduction pathway of vertebrate vision. Although the mechanism of activation of PDE by transducin is well understood, the role of the noncatalytic cGMP binding sites located on the catalytic subunits of PDE remains obscure. We report...
Article
The photoreceptor phosphodiesterase (PDE6) is the central effector enzyme in the phototransduction cascade of photoreceptor cells. It is the only known PDE isoform the activity of which is regulated by interaction with a heterotrimeric G protein. The rod PDE6 holoenzyme is a tetrameric protein consisting of two large catalytic alpha and beta subuni...
Article
Purpose The goal of this study is to determine the mechanism of action of E4021 (sodium l-[6-chloro-4-(3,4 methylene dioxybenzyl) amino-quinazolin-2-yl] piperidine-4-carboxylate sesquihydrate) on the frog rod photoreceptor phosphodiesterase (PDE). Methods. Purified frog rod outer segments were disrupted by homogenization. PDE activity assays were p...
Article
Purpose: The goal of this work is to define the factors that modulate the binding affinity of cGMP to noncatalytic sites on the catalytic subunits of the photoreceptor phosphodiesterase (PDE) Methods: Frog rod PDE was obtained from extracts of purified frog rod outer segments (ROS), and binding or dissociation assays were performed using a [3H]cGMP...
Article
Full-text available
A central step in vertebrate visual transduction is the rapid drop in cGMP levels that causes cGMP-gated ion channels in the photoreceptor cell membrane to close. It has long been a puzzle that the cGMP phosphodiesterase (PDE) whose activation causes this decrease contains not only catalytic sites for cGMP hydrolysis but also noncatalytic cGMP bind...
Article
Full-text available
This study examines the regulation of cGMP by illumination and by calcium during signal transduction in vertebrate retinal photoreceptor cells. We employed an electropermeabilized rod outer segment (EP-ROS) preparation which permits perfusion of low molecular weight compounds into the cytosol while retaining many of the features of physiologically...
Article
Full-text available
cGMP is the second messenger for visual excitation in vertebrate rod photoreceptors. However, no direct correlation has been observed between the measured total cGMP concentration in the rod outer segment and the electrical response of these cells to photic stimulation. To address this discrepancy, we have quantitated the number and affinities of c...
Article
In this review we have discussed the problem of deactivation at both the rhodopsin and G protein levels. Of particular interest is the novel observation that rhodopsin deactivation can be modulated by light. This modulation is likely to play an important role in light adaptation by reducing the gain of transduction. One interesting possibility is t...
Article
Full-text available
We have used a preparation of isolated, intact rod photoreceptors to correlate the effects of flash illumination on the intracellular cyclic GMP content and the membrane current. We find that the recovery of cyclic GMP levels after brief flash illumination requires approximately twice as much time as the recovery of the membrane current. In contras...
Article
Light causes a rapid, 1.7-fold increase in cyclic GMP concentration in intact squid retinas (Johnson et al. (1986]. To determine whether light-induced changes in cyclic GMP concentration result from activation of guanylate cyclase, we have studied the regulation of guanylate cyclase activity in squid (Loligo pealei) photoreceptors. The enzyme is me...
Article
Full-text available
Cyclic GMP has been implicated in controlling the light-regulated conductance of rod photoreceptors of the vertebrate retina. However, there is little direct evidence correlating changes in cGMP concentration with the light-regulated permeability mechanism in living cells. A preparation of intact frog rod outer segments suspended in a Ringer's medi...
Article
Full-text available
A rapid light-induced decrease in cGMP is thought to play a role in regulating the permeability or light sensitivity of photoreceptor membranes. Photo-excited rhodopsin activates a guanine nucleotide-binding protein (G-protein) by catalyzing the exchange of bound GDP for GTP. This G-protein X GTP complex activates the phosphodiesterase resulting in...
Article
Full-text available
This study examines whether changes in cGMP concentration initiated by illumination of frog rod photoreceptors occur rapidly enough to implicate cGMP as an intermediate between rhodopsin activation in the disc membrane and permeability changes in the plasma membrane. Previous studies using whole retinas or isolated outer segments have provided conf...
Article
The kinetics of microtubule polymerization to steady-state and the ability of tubulin subunits to exchange with polymer at steady-state were examined to determine the applicability of the head-to-tail polymerization mechanism (Wegner, 1976) to microtubule assembly in vitro. Under conditions where self-nucleation was a rare event, tubulin was induce...
Article
Full-text available
Treatment of gently prepared lysates of Escherichia coli with single-strand-specific endonuclease (SI or from mung beans) results in the release of about 90% of the DNA from membranes, as determined by the M band technique. The released DNA has an average molecular weight of about 1.2 X 10(8). Data obtained with endonuclease S1 fit a mathematical m...
Article
Full-text available
Mutants of Bacillus subtilis with altered deoxyribonucleic-dependent ribonucleic acid polymerase activity have been isolated and characterized. These mutants, selected as strains resistant to rifampin or streptolydigin, demonstrate drug-resistant in vitro ribonucleic acid synthesis. Sporeforming ability and support of phage infection are altered in...

Questions

Question (1)
Question
I have tried a few primary antibodies to detect His-tagged proteins on westerns, and been disappointed with the low signal intensity compared to other primary antibodies used in my lab. I would greatly appreciate hearing about anti-His antibodies that you can recommend I purchase.

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