Wnt-like pathways in Dictyostelium. During multicellular development, Dictyostelium cells first aggregate, then differentiate, into two main types of cells: prespore and prestalk cells. cAMP receptor cAR3 is dominant in prespore cells whereas cAR4 is dominant in prestalk cells. Thus, GSK3 activation prevails in prespore cells through the cAR3/ZAK1/ZAK2 module and is inhibited through the cAR4/PTPase module in prestalk cells. Unlike canonical Wnt signaling in the mammalian system in which GSK3 has a negative effect on beta-catenin, Dictyostelium beta-catenin ortholog Aardvark (Aar) is activated by GSK3 and stimulates prespore cell differentiation. B56 subunit of PP2A has an inhibitory effect on GSK3 activity, possibly either by inhibiting ZAK1/2 activities or via stimulating a protein tyrosine phosphatase [17]. Solid lines are supported by direct evidence, while dashed lines are suggested by circumstantial evidence.