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, 2 (1-2), 39-46

MAPKs in Development: Insights From Dictyostelium Signaling Pathways

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MAPKs in Development: Insights From Dictyostelium Signaling Pathways

Jeffrey A Hadwiger et al. Biomol Concepts.

Abstract

Mitogen activated protein kinases (MAPKs) play important roles in the development of eukaryotic organisms through the regulation of signal transduction pathways stimulated by external signals. MAPK signaling pathways have been associated with the regulation of cell growth, differentiation, and chemotaxis, indicating MAPKs contribute to a diverse set of developmental processes. In most eukaryotes, the diversity of external signals is likely to far exceed the diversity of MAPKs, suggesting that multiple signaling pathways might share MAPKs. Do different signaling pathways converge before MAPK function or can MAPKs maintain signaling specificity through interactions with specific proteins? The genetic and biochemical analysis of MAPK pathways in simple eukaryotes such as Dictyostelium offers opportunities to investigate functional specificity of MAPKs in G protein-mediated signal transduction pathways. This review considers the regulation and specificity of MAPK function in pathways that control Dictyostelium growth and development.

Figures

Figure 1
Figure 1
Typical MAPK signaling pathways. External signals can activate G protein-coupled receptors or receptor tyrosine kinases leading to the activation of MAPK cascades through several signaling steps. The activated MAPK can phosphorylate both cytoplasmic and nuclear targets to achieve cellular response.
Figure 2
Figure 2
Dendogram of selected ERKs from Dictyostelium discoideum (Dd), yeast (Saccharomyces cerevisiae; Sc) and mammals (Homo sapiens; Hs). Dendogram was generated at http://clustalw.genome.ed.jp/ by the neighbor-joining method from a ClustalW alignment. Branch lengths reflect sequence similarities.
Figure 3
Figure 3
Dictyostelium MAPK signaling downstream of three G protein-mediated signaling pathways. The cell surface receptors - folate receptor (FR), cAMP receptor (CAR), unknown receptor (R?) - couple to different Gα subunits and can activate one or both ERKs. ERK1 function is required for Gα5 subunit-pathway responses and ERK2 is required for Gα4 subunit-pathways responses. ERK2 can inhibit the cAMP specific phosphodiesterase, REGA, increasing the level of cAMP available for cell aggregation.

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