The bones behind the cytoskeleton network

A new cyclic adenosine monophosphate (cAMP) receptor called Epac (Exchange protein directly activated by cAMP) has been discovered by US scientists. Epac not only mediates the classic cAMP-dependent protein kinase system but also the intracellular cAMP actions.

Many water soluble hormones do not cross the cell membrane, but instead cause effects within the cell via a second messenger. cAMP is a second messenger that carries signals from the cell surface to proteins within the cell.

This study by Mei and Cheng of the University of Texas Medical Branch, US, opens up a new dimension in thinking about the connection between cAMP signalling and microtubule organisation. Cells contain a cytoskeleton network that is essential for maintaining normal cell structure and microtubules are critical components of the cytoskeleton.  

According to Mei and Cheng the in vivo and in vitro association of Epac with microtubules means that its cellular functions are closely related to the microtubule-associated cytoskeleton network.

Activation of Epac-mediated Rap1 is suppressed by association with microtubules, whereas the binding of Epac promotes microtubule formation. This demonstrates that Epac plays an important role in connecting the microtubule cytoskeleton network to intracellular cAMP-signalling.

This intimate relationship suggests that Epac may be associated with biological functions such as cell division, intracellular transport, cell motility, and cell morphology, in which the dynamic assembly and disassembly of microtubules is essential.

Epac may play an important role in coordinating these biological events by connecting the second messenger, cAMP, with the microtubule cytoskeleton network.

Joanne Bell