Mark Henry Pausch

Bio: Mark Henry Pausch is an academic researcher from American Cyanamid. The author has contributed to research in topics: G protein-coupled receptor & Receptor. The author has an hindex of 11, co-authored 21 publications receiving 2083 citations.

Evolving the lock to fit the key to create a family of G protein-coupled receptors potently activated by an inert ligand

Abstract: We evolved muscarinic receptors in yeast to generate a family of G protein-coupled receptors (GPCRs) that are activated solely by a pharmacologically inert drug-like and bioavailable compound (clozapine-N-oxide) Subsequent screening in human cell lines facilitated the creation of a family of muscarinic acetylcholine GPCRs suitable for in vitro and in situ studies We subsequently created lines of telomerase-immortalized human pulmonary artery smooth muscle cells stably expressing all five family members and found that each one faithfully recapitulated the signaling phenotype of the parent receptor We also expressed a Gi-coupled designer receptor in hippocampal neurons (hM4D) and demonstrated its ability to induce membrane hyperpolarization and neuronal silencing We have thus devised a facile approach for designing families of GPCRs with engineered ligand specificities Such reverse-engineered GPCRs will prove to be powerful tools for selectively modulating signal-transduction pathways in vitro and in vivo

ORK1, a potassium-selective leak channel with two pore domains cloned from Drosophila melanogaster by expression in Saccharomyces cerevisiae

Abstract: A K+ channel gene has been cloned from Drosophila melanogaster by complementation in Saccharomyces cerevisiae cells defective for K+ uptake. Naturally expressed in the neuromuscular tissues of adult flies, this gene confers K+ transport capacity on yeast cells when heterologously expressed. In Xenopus laevis oocytes, expression yields an ungated K(+)-selective current whose attributes resemble the "leak" conductance thought to mediate the resting potential of vertebrate myelinated neurons but whose molecular nature has long remained elusive. The predicted protein has two pore (P) domains and four membrane-spanning helices and is a member of a newly recognized K+ channel family. Expression of the channel in flies and yeast cells makes feasible studies of structure and in vivo function using genetic approaches that are not possible in higher animals.

Sequence and function of the two P domain potassium channels: implications of an emerging superfamily.

Abstract: A new superfamily of K+ channels has emerged in the past 2 years. Notable for possessing two pore-forming P domains in each subunit, members of the superfamily have been recognized through phylogeny from micro-organisms to humans. Four subfamilies of two P domain channels have been isolated thus far; among these are the first cloned examples of outward rectifier and open rectifier (or leak) K+ channels. The two P domain K+ channels offer a new perspective from which to glimpse the molecular basis for function and dysfunction of K+-selective ion channels.

Investigation of Growth Hormone Releasing Hormone Receptor Structure and Activity Using Yeast Expression Technologies

Abstract: Growth hormone releasing hormone (GHRH) is the positive regulator of growth hormone synthesis and secretion in the anterior pituitary. The peptide confers activity by binding to a seven transmembrane domain G protein-coupled receptor. Signal transduction proceeds through subsequent G alpha s stimulation of adenylyl cyclase. To investigate ligand/receptor and receptor/G protein associations, the human GHRH receptor was expressed in a modified S. cerevisiae strain which allows for facile measurement of receptor activity by cell prototrophy mediated by a reporter gene coupled to the yeast pheromone response pathway. GHRH-dependent signal activation in this system required the substitution of yeast G alpha protein with proteins containing C-terminal regions of G alpha s. A D60G variant (analogous to the little mouse mutation) of the receptor failed to respond to agonist. In parallel studies, GHRH29 and the N-terminal extracellular region of the receptor were expressed as Gal4 fusion proteins in a 2-hybrid assay. A specific interaction between these proteins was readily observed. The D60G mutation was engineered into the receptor fusion protein. This protein failed to interact with the ligand fusion, confirming the specificity of the association between unmodified proteins. These two yeast expression technologies should prove invaluable in additional structure/activity analyses of this ligand/receptor pair as well as other peptide ligands and receptors.

Global analysis of protein activities using proteome chips

Abstract: The present invention relates to proteome chips comprising arrays having a large proportion of all proteins expressed in a single species. The invention also relates to methods for making proteome chips. The invention also relates to methods for using proteome chips to systematically assay all protein interactions in a species in a high-throughput manner. The present invention also relates to methods for making and purifying eukaryotic proteins in a high-density array format. The invention also relates to methods for making protein arrays by attaching double-tagged fusion proteins to a solid support. The invention also relates to a method for identifying whether a signal is positive.

Rapid, reversible activation of AgRP neurons drives feeding behavior in mice

Abstract: Several different neuronal populations are involved in regulating energy homeostasis. Among these, agouti-related protein (AgRP) neurons are thought to promote feeding and weight gain; however, the evidence supporting this view is incomplete. Using designer receptors exclusively activated by designer drugs (DREADD) technology to provide specific and reversible regulation of neuronal activity in mice, we have demonstrated that acute activation of AgRP neurons rapidly and dramatically induces feeding, reduces energy expenditure, and ultimately increases fat stores. All these effects returned to baseline after stimulation was withdrawn. In contrast, inhibiting AgRP neuronal activity in hungry mice reduced food intake. Together, these findings demonstrate that AgRP neuron activity is both necessary and sufficient for feeding. Of interest, activating AgRP neurons potently increased motivation for feeding and also drove intense food-seeking behavior, demonstrating that AgRP neurons engage brain sites controlling multiple levels of feeding behavior. Due to its ease of use and suitability for both acute and chronic regulation, DREADD technology is ideally suited for investigating the neural circuits hypothesized to regulate energy balance.

Phylogenetic Relationships within Cation Transporter Families of Arabidopsis

Abstract: Uptake and translocation of cationic nutrients play essential roles in physiological processes including plant growth, nutrition, signal transduction, and development. Approximately 5% of the Arabidopsis genome appears to encode membrane transport proteins. These proteins are classified in 46 unique families containing approximately 880 members. In addition, several hundred putative transporters have not yet been assigned to families. In this paper, we have analyzed the phylogenetic relationships of over 150 cation transport proteins. This analysis has focused on cation transporter gene families for which initial characterizations have been achieved for individual members, including potassium transporters and channels, sodium transporters, calcium antiporters, cyclic nucleotide-gated channels, cation diffusion facilitator proteins, natural resistance-associated macrophage proteins (NRAMP), and Zn-regulated transporter Fe-regulated transporter-like proteins. Phylogenetic trees of each family define the evolutionary relationships of the members to each other. These families contain numerous members, indicating diverse functions in vivo. Closely related isoforms and separate subfamilies exist within many of these gene families, indicating possible redundancies and specialized functions. To facilitate their further study, the PlantsT database (http://plantst.sdsc.edu) has been created that includes alignments of the analyzed cation transporters and their chromosomal locations.