This service exclusively searches for literature that cites resources. Please be aware that the total number of searchable documents is limited to those containing RRIDs and does not include all open-access literature.
We applied G protein-derived beta gamma-subunits to permeabilized mast cells to test their ability to regulate exocytotic secretion. Mast cells permeabilized with streptolysin-O leak soluble (cytosol) proteins over a period of 5 min and become refractory to stimulation by Ca2+ and GTPgammaS over approximately 20-30 min. beta gamma-Subunits applied to the permeabilized cells retard this loss of sensitivity to stimulation (run-down) and it can be inferred that they interact with the regulatory mechanism for secretion. While alpha-subunits are without effect, beta gamma-subunits at concentrations >10(-8 )M enhance the secretion due to Ca2+ and GTPgammaS. Unlike the small GTPases Rac and Cdc42, beta gamma-subunits cannot induce secretion in the absence of an activating guanine nucleotide, and thus further GTP-binding proteins (likely to be Rho-related GTPases) must be involved. The enhancement due to beta gamma-subunits is mediated largely through interaction with pleckstrin homology (PH) domains. It remains manifest in the face of maximum activation by PMA and inhibition of PKC with the pseudosubstrate inhibitory peptide. Soluble peptides mimicking PH domains inhibit the secretion due to GTPgammaS and block the enhancement due to beta gamma-subunits. Our data suggest that beta gamma-subunits are components of the pathway of activation of secretion due to receptor-mimetic ligands such as mastoparan and compound 48/80.
Antisera directed against specific subunits of guanine nucleotide-binding regulatory proteins (G proteins) were used to immunoprecipitate these polypeptides from metabolically labeled cells. This technique detects, in extracts of a human astrocytoma cell line, the alpha subunits of Gs (stimulatory) (alpha 45 and alpha 52), a 41-kDa subunit of Gi (inhibitory) (alpha 41), a 40-kDa protein (alpha 40), and the 36-kDa beta subunit. No protein that comigrated with the alpha subunit of Go (unknown function) (alpha 39) was detected. In cells grown in the presence of [3H]myristic acid, alpha 41 and alpha 40 contained 3H label, while the beta subunit did not. Chemical analysis of lipids attached covalently to purified alpha 41 and alpha 39 from bovine brain also revealed myristic acid. Similar analysis of brain G protein beta and gamma subunits and of Gt (transducin) subunits (alpha, beta, and gamma) failed to reveal fatty acids. The fatty acid associated with alpha 41, alpha 40, and alpha 39 was stable to treatment with base, suggesting that the lipid is linked to the polypeptide via an amide bond. These GTP binding proteins are thus identified as members of a select group of proteins that contains myristic acid covalently attached to the peptide backbone. Myristate may play an important role in stabilizing interactions of G proteins with phospholipid or with membrane-bound proteins.
1. The action of GTP-binding proteins on ATP-sensitive potassium (KATP) channels was investigated. KATP channels were expressed in a mammalian cell line (COS-1 cells) by cotransfecting vectors carrying the sulphonylurea receptor (SUR1) and BIR (Kir6.2), a member of the inward rectifier K+ channel family. G proteins were also tested on KATP channels composed of an isoform of SUR1, SUR2A, in combination with Kir6.2. 2. The alpha and beta gamma subunits of the GTP binding protein G1 were tested separately in inside-out patches under continuous recording. G alpha-11 increases the activity of SUR1-Kir6.2 and SUR2A-Kir6.2 channels by 200 and by 30%, respectively. 3. G alpha-12 does not increase the activity of SUR1-Kir6.2 channels, but increase the activity of SUR2A-Kir6.2 channels by 30%. 4. Control experiments showed that GTP gamma S, a specific activator of G proteins, and heat-inactivated G alpha-11 do not increase the single channel activity. 5. No effects of the other subunits (beta gamma) from either G11 or G12 on the single channel activity were observed. 6. The protein kinase C inhibitors H7 and an inhibitory peptide (FARKGALRQKNV) had no effect on the modulatory action of G alpha-11 on SUR1-Kir6.2 channels. 7. We conclude that both types of reconstituted KATP channels are modulated by G proteins.
GTP binding regulatory protein (G protein)-coupled receptors can activate MAPK pathways via G protein-dependent and -independent mechanisms. However, the physiological outcomes correlated with the cellular signaling events are not as well characterized. In this study, we examine the involvement of G protein and beta-arrestin 2 pathways in kappa opioid receptor-induced, extracellular signal-regulated kinase 1/2 (ERK1/2)-mediated proliferation of both immortalized and primary astrocyte cultures. As different agonists induce different cellular signaling pathways, we tested the prototypic kappa agonist, U69593 as well as the structurally distinct, non-nitrogenous agonist, C(2)-methoxymethyl salvinorin B (MOM-Sal-B). In immortalized astrocytes, U69593, activated ERK1/2 by a rapid (min) initial stimulation that was sustained over 2 h and increased proliferation. Sequestration of activated Gbetagamma subunits attenuated U69593 stimulation of ERK1/2 and suppressed proliferation in these cells. Furthermore, small interfering RNA silencing of beta-arrestin 2 diminished sustained ERK activation induced by U69593. In contrast, MOM-Sal-B induced only the early phase of ERK1/2 phosphorylation and did not affect proliferation of immortalized astrocytes. In primary astrocytes, U69593 produced the same effects as seen in immortalized astrocytes. MOM-Sal-B elicited sustained ERK1/2 activation which was correlated with increased primary astrocyte proliferation. Proliferative actions of both agonists were abolished by either inhibition of ERK1/2, Gbetagamma subunits or beta-arrestin 2, suggesting that both G protein-dependent and -independent ERK pathways are required for this outcome.
The signal recognition particle and its receptor (SR) target nascent secretory proteins to the ER. SR is a heterodimeric ER membrane protein whose subunits, SRalpha and SRbeta, are both members of the GTPase superfamily. Here we characterize a 27-kD protein in Saccharomyces cerevisiae (encoded by SRP102) as a homologue of mammalian SRbeta. This notion is supported (a) by Srp102p's sequence similarity to SRbeta; (b) by its disposition as an ER membrane protein; (c) by its interaction with Srp101p, the yeast SRalpha homologue; and (d) by its role in SRP-dependent protein targeting in vivo. The GTP-binding site in Srp102p is surprisingly insensitive to single amino acid substitutions that inactivate other GTPases. Multiple mutations in the GTP-binding site, however, inactivate Srp102p. Loss of activity parallels a loss of affinity between Srp102p and Srp101p, indicating that the interaction between SR subunits is important for function. Deleting the transmembrane domain of Srp102p, the only known membrane anchor in SR, renders SR soluble in the cytosol, which unexpectedly does not significantly impair SR function. This result suggests that SR functions as a regulatory switch that needs to associate with the ER membrane only transiently through interactions with other components.
Welcome to the FDI Lab - SciCrunch.org Resources search. From here you can search through a compilation of resources used by FDI Lab - SciCrunch.org and see how data is organized within our community.
You are currently on the Community Resources tab looking through categories and sources that FDI Lab - SciCrunch.org has compiled. You can navigate through those categories from here or change to a different tab to execute your search through. Each tab gives a different perspective on data.
If you have an account on FDI Lab - SciCrunch.org then you can log in from here to get additional features in FDI Lab - SciCrunch.org such as Collections, Saved Searches, and managing Resources.
Here is the search term that is being executed, you can type in anything you want to search for. Some tips to help searching:
You can save any searches you perform for quick access to later from here.
We recognized your search term and included synonyms and inferred terms along side your term to help get the data you are looking for.
If you are logged into FDI Lab - SciCrunch.org you can add data records to your collections to create custom spreadsheets across multiple sources of data.
Here are the facets that you can filter your papers by.
From here we'll present any options for the literature, such as exporting your current results.
If you have any further questions please check out our FAQs Page to ask questions and see our tutorials. Click this button to view this tutorial again.
Year:
Count: