Why?  This paper contradicts 2 common “facts”:

1. Insulin-like Growth Factor-I Receptor (IGF-IR) signaling is anti-apoptotic, and

2. Activation of the Akt pathway leads to cell survival.

While true in most cases, the paper provides strong and convincing evidence that in some cases, the IGF-I (the ligand for the IGF-IR) sensitizes cells to apoptosis… AND this IGF-induced pro-apoptotic effect is mediated through the activation of Akt.

The paper sheds light on the complexity of the mysterious biological system called the “cell” by providing mechanistic justification for these apparent contradictions to the traditional roles of IGF-IR and Akt:

Apparently, the ability of the IGF-IR to signal both anti-apoptotic and pro-apoptotic signaling is dependent on the localization of the receptor in the plasma membrane (whether it is located inside or outside of membrane lipid rafts).

Isn’t that amazing!?

In cellular research, often times, we try to define the cell based on a number of characteristics or principles… but papers like the one mentioned above serve as prominent reminders that the cell is a dynamic system that does not always fit into the graphs and the Western Blot figures that we, as scientists, generate.

In case you are intrigued and would like to read this paper, here is a link:

Membrane Rafts Segregate Pro- from Anti-Apoptotic Insulin-Like Growth Factor-I Receptor Signaling in Colon Carcinoma Cells Stimulated by Members of the Tumor Necrosis Factor Superfamily by Maryse Remacle-Bonnet et al.

I have to warn you, it’s a long paper, and I am not sure I would read it all if it weren’t relevant to my research at this time.  However, for its conceptual value alone, it’s definitely worth examining.