Dictyostelium AMPKα regulates aggregate size and cell-type patterning.

Starved Dictyostelium cells aggregate into groups of nearly 10(5) cells. AMPK is a highly conserved serine/threonine protein kinase consisting of a catalytic and two regulatory subunits. As multi-cellular development in Dictyostelium is initiated upon starvation, we explored the role of the energy sensor, AMPK, which shows significant similarity to human AMPK and is expressed throughout development. Deletion of the ampkα gene results in the formation of numerous small-sized aggregates that develop asynchronously to form few fruiting bodies with small sori and long stalks. On the other hand, ampkα(OE) cells form fruiting bodies with small stalks and large sori when compared with wild-type, Ax2. A minimum of 5% ampkα(-) cells in a chimaera with Ax2 cells was sufficient to reduce the aggregate size. Also, the conditioned media collected from ampkα(-) cells triggered Ax2 cells to form smaller aggregates. The starved ampkα(-) cells showed low glucose levels and formed large aggregates when glucose was supplied exogenously. Interestingly, ampkα(-) cells exhibit abnormal cell-type patterning with increased prestalk region and a concomitant reduction of prespore region. In addition, there was a loss of distinct prestalk/prespore boundary in the slugs.