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Published on: May 12, 2015
Pak1 and its T212 phosphorylated form accumulate in neurones and epithelial cells of the developing rodent
Julia L Zhong1, Monisha D Banerjee, Margareta Nikolic
1Developmental Neurobiology MRC Centre, King's College London, London, United Kingdom.
Abstract:
The serine/threonine kinase Pak1 is a target of the RhoGTPases Rac and Cdc42 and an important regulator of cell morphology and migration. Recent work from several laboratories has indicated that Pak1 controls microtubule dynamics as well as the organisation of F-actin microfilaments. Pak1 is phosphorylated on T212 by the p35/Cdk5 or cyclin B1/Cdc2 kinase in postmitotic neurones and mitotic cells, respectively. To understand its function during development, we have carried out a detailed temporal and spatial analysis of Pak1 expression and phosphorylation on T212. In the embryonic forebrain, Pak1 and Pak1T212(PO4) were seen to accumulate in the corpus callosum, intermediate zone, lateral olfactory tracts, and anterior commissures. Epithelial cells of the mouse embryo lung, kidney, intestine, and skin also exhibited high levels of Pak1 and Pak1T212(PO4), suggesting a previously unsuspected role in epithelial differentiation. Pak1T212(PO4) was undetectable in all adult tissues. Together, these data indicate a specific, developmentally regulated role of the Pak1 kinase.
Insights
The serine/threonine kinase Pak1 plays a crucial role in embryonic development, particularly in brain and epithelial tissues. Its specific phosphorylation pattern, Pak1T212(PO4), is developmentally regulated and absent in adults.
Area of Science:
- Cell Biology
- Developmental Biology
- Neuroscience
Background:
- Pak1 (p21-activated kinase 1) is a serine/threonine kinase regulated by Rho GTPases.
- Pak1 influences cell morphology, migration, and cytoskeletal organization (microtubules and F-actin).
- Pak1 is phosphorylated at T212 by Cdk5 or Cdc2 kinases in specific cell types.
Purpose of the Study:
- To investigate the temporal and spatial expression of Pak1 and its T212 phosphorylation during embryonic development.
- To elucidate the developmental roles of Pak1 kinase activity.
Main Methods:
- Analysis of Pak1 and Pak1T212(PO4) expression patterns in embryonic tissues.
- Immunohistochemical localization of Pak1 and its phosphorylated form.
Main Results:
- Pak1 and Pak1T212(PO4) were detected in specific embryonic brain regions (corpus callosum, intermediate zone, olfactory tracts, anterior commissures).
- High levels of Pak1 and Pak1T212(PO4) were observed in embryonic epithelial cells (lung, kidney, intestine, skin), suggesting a role in differentiation.
- Pak1T212(PO4) was not detected in any adult tissues examined.
Conclusions:
- Pak1 exhibits a specific, developmentally regulated expression and phosphorylation pattern.
- Pak1 kinase activity, indicated by T212 phosphorylation, appears critical for embryonic development, particularly in neural and epithelial tissues.
- The absence of Pak1T212(PO4) in adult tissues suggests its role is primarily confined to developmental processes.
