The RAF saga continues

RAF Inhibitors Activate the MAPK Pathway by Relieving Inhibitory Autophosphorylation

Cancer Cell, Volume 23, Issue 5, 594-602, 13 May 2013

http://www.sciencedirect.com/science/article/pii/S1535610813001347

(Also comment at http://www.sciencedirect.com/science/article/pii/S1535610813001347)

People in this field have been trying to figure out why RAF drugs induce the Erk MAPK pathway. This paper reports a new mechanism for RAF regulation and MAPK activation. Normally p-loop autphosphorylation (in trans as a dimer) of RAF inhibits the kinase. By adding low amounts of the inhibitors they developed, one of the monomers remains unphosphorylated and can activate the MEK-ERK pathway. But if they add even more inhibitor, both monomers are inhibited. Pretty neat.

p38-mediated senescence

A Posttranslational Modification Cascade Involving p38, Tip60, and PRAK Mediates Oncogene-Induced Senescence

Molecular Cell, 16 May 2013

http://www.sciencedirect.com/science/article/pii/S1097276513002943

I'm glad the authors defined the word "senescence" in the first sentence. I had also never heard of PRAK or Tip60, so I was off to a pretty bad start with this paper. Fortunately it was pretty straightforward: they used yeast-two-hybrid to find that Tip60 interacts with the kinase PRAK. Then they did a ton of experiments (manifested by an even greater number of western blots) to show that ras-activated p38 phosphorylates both PRAK and Tip60, which also acetylates PRAK. These modifications activate PRAK, which has pro-senescent properties.

Cell-Penetrating Bisubstrate-Based Protein Kinase C Inhibitors

ACS Chem. Biol., Article ASAP

http://pubs.acs.org/doi/full/10.1021/cb300709g

This article tries to tackle the kinase selectivity problem through a bivalent approach that targets the adenosine pocket and a substrate binding groove with one ligand. Bivalent inhibitors have been around for a while, but their main problem is lack of cell permeability. The authors in this paper address this issue by using cell-penetrating peptides (CPP) in an effort to target PKC. Looks like they got single-digit micromolar inhibition and good selectivity, plus cell permeability.

mTOR revealed

mTOR kinase structure, mechanism and regulation

Nature

 

497,

 

193–194

 

(09 May 2013)

http://www.nature.com/nature/journal/v497/n7448/full/nature12101.html

Some incredible structures reported in this paper. mTOR has been a really hot topic for several years, so it's great to see some intense structural biology on this kinase. Fire up pymol and have fun with these structures.

Prevention of Erk2 activation via protein-protein interaction

Interaction with Shc prevents aberrant Erk activation in the absence of extracellular stimuli

Nature Structural & Molecular Biology

 

20,

 

620–627

 

(2013)

http://www.nature.com/nsmb/journal/v20/n5/full/nsmb.2557.html

Neat paper on how the protein Shc prevents Erk activation. Apparently Shc binds directly to Erk, but then dissociates upon activation of EGFR. No x-ray structure of the complex, but a SAXS model showed the phosphotyrosine-binding domain of Shc clamping onto the N-lobe of Erk. From a mechanistic standpoint, I wonder how Shc binding prevents Erk phosphorylation by MEK. 

Detailed PKA mechanism analysis by xray

Phosphoryl Transfer by Protein Kinase A Is Captured in a Crystal Lattice

J. Am. Chem. Soc., 2013, 135 (12), pp 4788–4798

DOI: 10.1021/ja312237q

http://pubs.acs.org/doi/full/10.1021/ja312237q

Nice paper where the authors show phosphoryl transfer on an atomic scale. Pretty neat that the supposedly non-hydrolyzable ATP (AMP-PNP) was actually a capable co-substrate. Also interesting how slow catalysis occurs in the crystal lattice, judging from the fact that they essentially performed a crystallographic timecourse experiment over several months.

Hello world

This blog is going to be about recent protein kinase literature. While the aims of other kinase blogs (kinasepro, another kinasepro) appeared to focus mainly on kinase drug development information, I will take a more broad approach and try to cover basically any kinase paper that I come across. Hope you enjoy it!