Segregation of Heterotrimeric G Proteins in Cell Surface Microdomains: Gq Binds Caveolin to Concentrate in Caveolae, whereas Gi and Gs Target Lipid Rafts by Default

Select lipid-anchored proteins such as glycosylphosphatidylinositol (GPI)-anchored proteins and nonreceptor tyrosine kinases may preferentially partition into sphingomyelin-rich and cholesterol-rich plasmalemmal microdomains, thereby acquiring resistance to detergent extraction. Two such domains, caveolae and lipid rafts, are morphologically and biochemically distinct, contain many signaling molecules, and may function in compartmentalizing cell surface signaling. Subfractionation and confocal immunofluorescence microscopy reveal that, in lung tissue and in cultured endothelial and epithelial cells, heterotrimeric G proteins (Gi, Gq, Gs, and Gβγ) target discrete cell surface microdomains. Gq specifically concentrates in caveolae, whereas Gi and Gs concentrate much more in lipid rafts marked by GPI-anchored proteins (5′ nucleotidase and folate receptor). Gq, apparently without Gβγ subunits, stably associates with plasmalemmal and cytosolic caveolin. Gi and Gs interact with Gβγ subunits but not caveolin. Gi and Gs, unlike Gq, readily move out of caveolae. Thus, caveolin may function as a scaffold to trap, concentrate, and stabilize Gq preferentially within caveolae over lipid rafts. In N2a cells lacking caveolae and caveolin, Gq, Gi, and Gs all concentrate in lipid rafts as a complex with Gβγ. Without effective physiological interaction with caveolin, G proteins tend by default to segregate in lipid rafts. The ramifications of the segregated microdomain distribution and the Gq-caveolin complex without Gβγ for trafficking, signaling, and mechanotransduction are discussed.

G protein subunits and the stimulation of phospholipase C by Gs-and Gi-coupled receptors: Lack of receptor selectivity of Galpha(16) and evidence for a synergic interaction between Gbeta gamma and the alpha subunit of a receptor activated G protein.

Stimulatory guanine nucleotide binding protein (Gs)-coupled receptors activated by luteinizing hormone, vasopressin, and the catecholamine isoproterenol (luteinizing hormone receptor, type 2 vasopressin receptor, and types 1 and 2 beta-adrenergic receptors) and the Gi-coupled M2 muscarinic receptor (M2R) were expressed transiently in COS cells, alone and in combination with Gbeta gamma dimers, their corresponding Galphas (Galpha(s), or Galpha(i3)) and either Galpha(q) or Galpha(16). Phospholipase C (PLC) activity, assessed by inositol phosphate production from preincorporated myo[3H]inositol, was then determined to gain insight into differential coupling preferences among receptors and G proteins. The following were observed: (i) All receptors tested were able to stimulate PLC activity in response to agonist occupation. The effect of the M2R was pertussis toxin sensitive. (ii) While, as expected, expression of Galpha(q) facilitated an agonist-induced activation of PLC that varied widely from receptor to receptor (400% with type 2 vasopressin receptor and only 30% with M2R), expression of Galpha(16) facilitated about equally well the activation of PLC by any of the tested receptors and thus showed little if any discrimination for one receptor over another. (iii) Gbeta gamma elevated basal (agonist independent) PLC activity between 2- and 4-fold, confirming the proven ability of Gbeta gamma to stimulate PLCbeta. (iv) Activation of expressed receptors by their respective ligands in cells coexpressing excess Gbeta gamma elicited agonist stimulated PLC activities, which, in the case of the M2R, was not blocked by pertussis toxin (PTX), suggesting mediation by a PTX-insensitive PLC-stimulating Galpha subunit, presumably, but not necessarily, of the Gq family. (v) The effects of Gbeta gamma and the PTX-insensitive Galpha elicited by M2R were synergistic, suggesting the possibility that one or more forms of PLC are under conditional or dual regulation of G protein subunits such that stimulation by one sensitizes to the stimulation by the other.

Perceptions Surrounding the Implementation of Colorado Senate Bill 10-191's New Teacher Evaluations

In 2013, many public education reform efforts in the United States of America center on testing and accountability. Recent data revealed that teachers have the single greatest in-school impact on student learning; however, the methods to assess teacher effectiveness are widely criticized for not holding teachers accountable and, consequently, are experiencing significant legislative attention. In 2010, Colorado passed Senate Bill 10-191: The Great Teachers and Leaders Act to improve student learning by revising teacher and principal evaluations, including linking them to student learning data, and eradicating tenure. Teachers, administrators, and policymakers hold critical roles in the implementation of this bill, yet little is known about how members of each group perceive their respective roles in the implementation. This explanatory sequential mixed methods study was designed to gather perception data from these three groups, through surveys and interviews. Data revealed that teachers and administrators do not have similar perceptions of many matters related to teacher evaluations, education reform, and the implementation of Senate Bill 10-191 (SB 191). The data also revealed that teachers and administrators expected they would agree on these matters. These collective findings led to multiple recommendations, such as the need for increased dialogue between teachers and administrators about their own perceptions of education reforms.

Bill to Harvard College from Bartholomew Green, 1723 November 19

This bill was rendered to Harvard College by Bartholomew Green for costs related to the printing of the Library Catalogue. The verso contains a receipt for payment signed by Green on January 11, 1723/4.

Bill to Harvard College from Samuel Gerrish, 1723 December 10

This bill was rendered to Harvard College by Samuel Gerrish for costs related to the printing of the Library Catalogue. The verso contains a receipt for payment signed by Gerrish on January 6, 1723/4.

Bill to Harvard College from Samuel Gerrish, 1725 June 11

This bill was rendered to Harvard College by Samuel Gerrish for costs related to the printing of the Library Catalogue supplement.

Bill from Phillips Payson to Harvard College, [1780 August]

This undated bill was rendered to the College by Phillips Payson (died 1809; Harvard AB 1778) for work done in the College Library equaling £720. The document was originally housed in a folder with the note, "This was from the old trunk."

Quarter bill book for the Classes of 1689-1723 and ledger, 1687-1720

Parchment hardcover bound volume arranged into two parts: Quarter bill book and the Steward's ledger. The Quarter bill book contains quarter bill tallies for the Classes of 1689-1723 arranged by seniority, and covers the bill period ending on October 21, 1687 through the period ending March 11, 1720.

Quarter bill book for the Classes of 1720-1760, 1720-1756

Parchment hardcover bound volume containing quarter bill tallies for the Classes of 1720-1760 arranged by seniority, and covering the bill period ending on June 10, 1720 through the period ending December 10, 1756. After each quarter's tallies, an additional section provides the totals for all students in each of the categories, and deductions for building repairs.