AGS proteins and nucleic acid molecules and uses thereof

Details AGS proteins and nucleic acid molecules and uses thereof AGS proteins and nucleic acid molecules and uses thereof

1999-11-11

2004-06-08

Priebe, Scott D. (Department: 1635)

Chemistry: molecular biology and microbiology

Micro-organism, tissue cell culture or enzyme using process...

Recombinant dna technique included in method of making a...

C435S252300, C435S254200, C435S325000, C435S455000, C435S320100, C536S023500, C536S024100, C536S023100

Reexamination Certificate

active

06746852

ABSTRACT:

Throughout this application, various publications are referenced by author and date. Full citations for these publications may be found throughout the specification. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art as known to those skilled therein as of the date of the invention described and claimed herein.
BACKGROUND OF THE INVENTION
Heterotrimeric G protein-mediated signal transduction is a tightly regulated event. All known G protein-coupled receptor (GPCR) mediated signaling pathways rely on multiple regulatory mechanisms in order to prevent inappropriate induction of the signal and to facilitate recovery during chronic stimulation (Gilman (1987)
Ann. Rev. Biochem
. 56:615-649, reviewed in Simon et al. (1991)
Science
252:802-808; Conklin and Bourne (1993)
Cell
73:631-641; Neer (1995)
Cell
80
:
249
-
257
; Rens-Domiano and Hamm (1995)
FASEB J
. 9:1059-1066). These regulatory mechanisms function at every level of the signaling cascade. Regulation of GPCR activation is believed to involve phosphorylation of the receptor C-terminus and subsequent receptor internalization (Palczewski and Benkovic (1991)
Trends Biol. Sci
. 16:387-391; Goodman et al. (1996)
Nature
383:447-450; Chen and Konopka (1996)
Mol. Cell. Biol
. 16:247-257), though this does not appear to be a universal mechanism (Daunt et al. (1997)
Mol. Pharm
. 51:711-720). Known mechanisms of regulation of signal transduction at the level of the heterotrimeric G protein include receptor-mediated facilitation of GTP/GDP exchange on G&agr; (reviewed in Simon et al. (1991)
Science
252:802-808; Conklin and Bourne (1993)
Cell
73:631-641; Neer (1995)
Cell
80:249-257; Rens-Domiano and Hamm (1995)
FASEB J
. 9:1059-1066) and enhancement of the intrinsic GTPase activity of G&agr; proteins by RGS-like proteins (reviewed in Berman and Gilman (1998)
J. Biol. Chem
. 273:1269-1272). Activation of PAKs, serine/threonine kinases that transduce signals from heterotrimeric G proteins to the MAP kinase cascade, has been shown to occur through interaction with either the small G proteins Cdc42 and Rac, or through interaction with heterotrimeric G proteins (reviewed in Sells and Chernoff (1997)
Trends Cell Biol
. 7:162-167). GPCR-coupled MAP kinase cascades and their downstream transcription factors, in turn, are regulated through phosphorylation/dephosphorylation cycles that may or may not require small G proteins (reviewed in Cobb and Goldsmith (1995)
J. Biol. Chem
. 270:14843-14846). (Strittmatter et al. (1993)
Proc. Nat'l Acad. Sci., USA
90:5327-5331; Okamoto et al. (1995)
J. Biol. Chem
. 27:4205-4208; Sato et al. (1996)
J. Biol. Chem
. 271:30052-30060) and non-protein activtors (summarized in Odagaki et al. (1998)
Life Sciences
62:1537-1541.
Even with the identification of these diverse regulatory systems, an in-depth understanding of the temporal and spatial regulation of GPCR mediated signaling remains elusive. In fact, cellular variations in the efficiency and/or specificity of coupling observed for many specific receptor-heterotrimeric G protein complexes suggest the presence of additional unidentified, cell-specific regulators of the signaling process.
SUMMARY OF THE INVENTION
In an attempt to identify novel factors involved in regulating signaling through GPCR-mediated signal transduction pathways, a screening system was devised in the yeast
Saccharomyces cerevisiae
designed to identify receptor-independent activators of the pheromone response pathway. These functional screens can be designed to target not only specific regulatory pathways in yeast, but also an introduced mammalian component or components. Yeast strains containing an intact signal transduction cascade but lacking a functional GPCR were made conditional for growth upon either pheromone pathway activation (activator screen) or pheromone pathway inactivation (inhibitor screen). In addition, the activator yeast strain carries an integrated FUS1p-HIS3 construct, making histidine prototrophy conditional upon pheromone pathway activation. The inhibitor yeast strain carries an episomal FUS1p-CAN1 construct. Adult human liver cDNAs expressed in a yeast vector under control of a galactose-inducible promoter were introduced into these strain, and those cDNAs that conferred growth in a galactose- and insert-dependent fashion were identified. Provided herein is the characterization of one member of these activator cDNAs, encoding a protein of 281 amino acids with significant homology to ras-related G proteins and containing alterations in conserved amino acids consistent with a deficiency in GTP hydrolysis activity (i.e., a constitutively active form of ras-related G protein). Genetic epistasis tests in yeast were consistent with this activator functioning at the level of the heterotrimeric G-protein and facilitating GTP exchange on the chimeric G&agr;i2. This protein is referred to herein as Activator of G protein Signaling, or “AGS”, or AGS1-AGS1 also shows G&agr; selectivity, as measured by constructs, and tissue specific expression, as measured by Northern blot analysis. A cDNA product identified from the inhibitor screen encodes a previously identified regulator of G-protein signaling, human RGS5.
In one embodiment, an isolated nucleic acid molecule of the present invention encodes an AGS protein (e.g., the nucleic acid molecule has a nucleotide sequence having at least 86% homology with the nucleotide sequence of SEQ ID NO:1 or the complement thereof).
In another embodiment, an isolated nucleic acid molecule of the present invention has a nucleotide sequence having at least 90% homology with the nucleotide sequence of SEQ ID NO:1 or SEQ ID NO:3, or the complement of SEQ ID NO:1 or SEQ ID NO:3.
In yet another embodiment, the isolated nucleic acid molecule has the nucleotide sequence of SEQ ID NO:1, or the complement thereof.
In another embodiment, the isolated nucleic acid molecule has the nucleotide sequence of SEQ ID NO:3, or the complement thereof.
In yet another embodiment, an isolated nucleic acid molecule of the present invention encodes a protein that activates G protein-coupled signal transduction in a G protein-coupled receptor independent manner.
In another embodiment, an isolated nucleic acid molecule of the present invention has a nucleotide sequence which encodes a protein having an amino acid sequence at least 97% identical to the amino acid sequence of SEQ ID NO:2. In another embodiment, the isolated nucleic acid molecule encodes a protein having the amino acid sequence of SEQ ID NO:2.
In yet another embodiment, an isolated nucleic acid molecule of the present invention encodes a protein which activates G protein-coupled signal transduction in a G protein-coupled receptor independent manner.
The present invention also provides vectors including nucleic acid sequences which encode all or a portion of an AGS protein as well as host cells including such vectors.
The invention further provides methods for producing an AGS protein including culturing host cells which express an AGS protein.
The invention also provides transgenic animals which contain cells carrying a transgene encoding AGS protein.
In another embodiment, the present invention provides isolated AGS proteins (e.g., an isolated AGS protein having an amino acid sequence at least 97% homology with the amino acid sequence of SEQ ID NO:2.)
In another embodiment, the protein has the amino acid sequence of SEQ ID NO:2.
The present invention also provides fusion proteins having at least a portion of an AGS protein operatively linked to a non-AGS polypeptide as well as antibodies that specifically bind to an AGS protein (e.g., monoclonal or polyclonal antibodies).
The invention further provides pharmaceutical compositions including AGS proteins or AGS-antibodies.
The present invention further provides methods for identifying compounds that modulate cellular signal transduction.
In one embodiment, the method includes the steps of (a) contacting a cell

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