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Updated: Sep 28, 2026
Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development
Published on: June 15, 2017
Mbt, a Drosophila PAK protein, combines with Cdc42 to regulate photoreceptor cell morphogenesis
Daniela Schneeberger1, Thomas Raabe
1University of Würzburg, Institut für Medizinische Strahlenkunde und Zellforschung (MSZ), Versbacherstr. 5, 97078 Würzburg, Germany.
Abstract:
The Drosophila gene mushroom bodies tiny (mbt) encodes a putative p21-activated kinase (PAK), a family of proteins that has been implicated in a multitude of cellular processes including regulation of the cytoskeleton, cell polarisation, control of MAPK signalling cascades and apoptosis. The mutant phenotype of mbt is characterised by fewer neurones in the brain and the eye, indicating a role of the protein in cell proliferation, differentiation or survival. We show that mutations in mbt interfere with photoreceptor cell morphogenesis. Mbt specifically localises at adherens junctions of the developing photoreceptor cells. A structure-function analysis of the Mbt protein in vitro and in vivo revealed that the Mbt kinase domain and the GTPase binding domain, which specifically interacts with GTP-loaded Cdc42, are important for Mbt function. Besides regulation of kinase activity, another important function of Cdc42 is to recruit Mbt to adherens junctions. We propose a role for Mbt as a downstream effector of Cdc42 in photoreceptor cell morphogenesis.
Insights
The Drosophila gene mushroom bodies tiny (mbt) protein is crucial for photoreceptor cell development. It acts as a downstream effector of Cdc42, regulating cell morphogenesis by localizing to adherens junctions.
Area of Science:
- Developmental Biology
- Cell Biology
- Genetics
Background:
- The Drosophila mushroom bodies tiny (mbt) gene encodes a p21-activated kinase (PAK).
- PAK proteins are involved in cytoskeletal regulation, cell polarity, MAPK signaling, and apoptosis.
- mbt mutants exhibit reduced neuron numbers, suggesting roles in cell proliferation, differentiation, or survival.
Purpose of the Study:
- To investigate the function of the mbt gene in Drosophila development.
- To elucidate the role of Mbt protein in photoreceptor cell morphogenesis.
- To understand the interaction between Mbt and Cdc42 in cellular processes.
Main Methods:
- Analysis of mbt mutant phenotypes in Drosophila.
- Localization studies of Mbt protein in developing photoreceptor cells.
- In vitro and in vivo structure-function analysis of Mbt protein domains.
- Investigation of Mbt interaction with Cdc42.
Main Results:
- Mutations in mbt disrupt photoreceptor cell morphogenesis.
- Mbt protein localizes to adherens junctions in developing photoreceptor cells.
- The kinase domain and GTPase binding domain of Mbt are essential for its function.
- Cdc42 binding and recruitment of Mbt to adherens junctions are critical.
Conclusions:
- Mbt plays a significant role in photoreceptor cell morphogenesis.
- Mbt functions as a downstream effector of Cdc42.
- Cdc42 regulates Mbt localization and activity at adherens junctions.
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