Dictyostelium AMPKα regulates aggregate size and cell-type patterning

Abstract

Starved Dictyostelium cells aggregate into groups of nearly 105 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 ampka 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, ampkaOE cells form fruiting bodies with small stalks and large sori when compared with wild-type, Ax2. A minimum of 5% ampka2 cells in a chimaera with Ax2 cells was sufficient to reduce the aggregate size. Also, the conditioned media collected from ampka2 cells triggered Ax2 cells to form smaller aggregates. The starved ampka2 cells showed low glucose levels and formed large aggregates when glucose was supplied exogenously. Interestingly, ampka2 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.