Talk:Sterol regulatory element-binding protein

Untitled

In mammalian cells, sterol regulatory element-binding proteins (SREBPs) coordinate metabolic flux through the cholesterol and fatty acid biosynthetic pathways in response to intracellular cholesterol levels. We describe experiments that evaluate the functional equivalence of mammalian SREBPs and the insect homologue of SREBP-1a, HLH106, in both mammalian and insect cell culture systems. HLH106 binds to both palindromic E-boxes and direct repeat sterol regulatory elements (SREs) efficiently, suggesting that it has a dual DNA binding specificity similar to the mammalian proteins. The amino-terminal "mature" protein activates transcription from mammalian SREs in both mammalian and Drosophila tissue culture cells. Additionally, HLH106 also requires a ubiquitous regulatory co-activator to efficiently activate transcription from mammalian SREs. These properties are shared with its mammalian counterparts. When expressed in mammalian cells, the carboxyl-terminal portion also localizes to perinuclear membranes similar to mammalian SREBPs. Furthermore, membrane-bound HLH106 is proteolytically processed in response to intracellular sterol levels in mammalian cells in an SREBP cleavage-activating protein-stimulated fashion. The presence of an SREBP homologue in Drosophila whose processing is regulated by intracellular sterol levels when expressed in mammalian cells suggests that related processing machinery exists in insect cells. This is notable, since insects are reportedly incapable of de novo sterol biosynthesis.

Prashant kumar , consultant , CADD Group , Connexios life scinece Pvt Ltd , No49 Shilpa Vidhya 1st main , JP nagar Bangalore-78 , India , email: prashantkbio@gmail.com

SREBP SCAP Image

The image explaining the operation of SREBPs and SCAP is good, but too small. Could we get a larger version so that the text can be read. Thanks :D

Found the original jpg and converted into higher resolution png. Cheers Boghog2 (talk) 23:18, 21 November 2007 (UTC)

Article organization

This article is not as much structured like an encyclopedia page but more like a research manuscript. It may be good to first clearly explain (to the depth of current medical knowledge) the purpose of SREBPs and then some of the history. Great info, just could be arranged better for understanding. 68.35.194.40 22:32, 12 April 2007 (UTC)

Start out article with a simple statement of what SREBP is, rather than starting out with its history.

I have made a start on reorganizing this article which I hope makes it more encyclopedic. However additional editing, especially by an expert on SREBP would be greatly appreciated. Cheers. Boghog2 (talk) 12:27, 17 November 2007 (UTC)

Sterol Biosynthesis or Sterol-Receptor Biosynthesis?

To my understanding, SREBPs activate synthesis of enzymes involved in production of sterol RECEPTORS, rather than those that directly synthesize sterols. In the abstract of the article cited as [3] you can read that a fraction of SREBP activates transcription of the genes for the LDL receptor.

http://dx.doi.org/10.1016/0092-8674(94)90234-8

At the link

http://en.wikipedia.org/wiki/LDL

Under the title "LDL import to the cell", you can see that when a cell requires cholesterol, it synthesizes the necessary LDL receptors. I have the feeling that your sentence mislead that concept.

"These activated SREBPs then bind to specific sterol regulatory element DNA sequences which upregulate the synthesis of enzymes involved in sterol biosynthesis". Similarly the following sentence can mislead: "Sterols in turn inhibit the cleavage of SREBPs and therefore synthesis of additional sterols".

Of course I can be wrong, please let me know if that is the case.

Lipidstudent (talk) 17:17, 6 December 2007 (UTC)

Thanks for your note. It appears that we both may be right. From the abstract you cite: This fragment ... activates transcription of the genes for the LDL receptor and HMG CoA synthase. Please feel free to edit the article to include upregulation of LDL receptors. Cheers. Boghog2 (talk) 19:00, 6 December 2007 (UTC)

PPAR-a and SREBP1-c

I think the sentence " PPARα agonists act in cooperation with LXR or insulin to induce lipogenesis.[9]" is not correct, because PPARa induce lipolysis and not lipogenesis! — Preceding unsigned comment added by 151.42.168.241 (talk) 09:41, 1 June 2012 (UTC)