GSN

GSN may refer to:

Game Show Network

Game Show Network (GSN) is an American digital cable and satellite television channel that is owned as a joint venture between Sony Pictures Television (owning a controlling 58% interest) and AT&T Inc. (holding a 42% ownership stake).

The channel's programming is primarily dedicated to game shows, including reruns of classic game shows, along with new, first-run original and revived game shows. For a period in the mid-2000s, Game Show Network began branching out into "games" in general, including reality competition series and televised poker shows.

As of February 2015, approximately 79,471,000 American households (68.3% of households with television) receive GSN.

History

Pre-launch

On May 7, 1992, Sony Pictures Entertainment joined forces with the United Video Satellite Group to launch Game Show Channel, which was set to launch in 1993. The announcement of the channel was made by SPE president Mel Harris. Sony Pictures' holdings included those by Merv Griffin Enterprises and Barris Industries, Inc. SPE was in competition with The Family Channel in launching a game show-oriented channel when The Family Channel announced the launch of its own service called Game Channel.

Gelsolin

Gelsolin is an actin-binding protein that is a key regulator of actin filament assembly and disassembly. Gelsolin is one of the most potent members of the actin-severing gelsolin/villin superfamily, as it severs with nearly 100% efficiency. Gelsolin is located intracellularly (in cytosol and mitochondria) and extracellularly (in blood plasma).

Structure

Gelsolin is an 82-kD protein with six homologous subdomains, referred to as S1-S6. Each subdomain is composed of a five-stranded β-sheet, flanked by two α-helices, one positioned perpendicular with respect to the strands and one positioned parallel. The N-terminal (S1-S3) forms an extended β-sheet, as does the C-terminal (S4-S6).

Regulation

Among the lipid-binding actin regulatory proteins, gelsolin (along with cofilin) is one of the few that exhibit preferential binding toward polyphosphoinositide (PPIs). The binding sequences in gelsolin closely resemble the motifs in the other PPI-binding proteins.

Gelsolin's activity is stimulated by calcium ions (Ca²⁺). Although the protein retains its overall structural integrity in both activated and deactivated states, the S6 helical tail moves like a latch depending on the concentration of calcium ions. The C-terminal end detects the calcium concentration within the cell. When there is no Ca²⁺ present, the tail of S6 shields the actin-binding sites on one of S2's helices. When a calcium ion attaches to the S6 tail, however, it straightens, exposing the S2 actin-binding sites. The N-terminal is directly involved in the severing of actin. S2 and S3 bind to the actin before the binding of S1 severs actin-actin bonds and caps the barbed end.