Mechanism of Aggregation in Dictyostelium
The mechanism behind the aggregation of the amoebae relies on Cyclic adenosine monophosphate (cAMP) as a signal molecule. One cell, the founder of the colony, begins to secrete cAMP in response to stress. Others detect this signal, and respond in two ways:
- The amoeba moves towards the signal.
- The amoeba secretes more cAMP to boost the signal.
The effect of this is to relay the signal throughout the nearby population of amoebae and cause inward movement to the area of highest cAMP concentration.
Within an individual cell, the mechanism is as follows:
- cAMP reception at the cell membrane activates a G-protein
- G protein stimulates Adenylate cyclase
- cAMP diffuses out of cell into medium
- Internal cAMP inactivates the external cAMP receptor.
- A different g-protein stimulates Phospholipase C
- IP3 induces calcium ion release
- Calcium ions act on the cytoskeleton to induce the extension of pseudopodia.
Because the internal cAMP concentration inactivates the receptor for external cAMP, an individual cell shows oscillatory behaviour. This behaviour produces beautiful spirals seen in converging colonies and is reminiscent of the Belousov-Zhabotinsky reaction and two-dimensional cyclic cellular automata.
Read more about this topic: Dictyostelid
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