Dual lipidation of the brain-specific Cdc42 isoform regulates its functional properties

Abstract

Cdc42 (cell division cycle 42) is a member of the Rho GTPase family which regulates a variety of cellular activities by controlling actin cytoskeleton and gene expression. Cdc42 is expressed in the form of two splice variants. The canonical Cdc42 isoform is prenylated (Cdc42-prenyl), whereas the brainspecific isoform can be palmitoylated (Cdc42-palm). In the present study we have demonstrated palmitoylation of endogenous Cdc42 in rodent and human brains and identified Cys(188) and Cys(189) as acylation sites of Cdc42-palm. Moreover, we have shown that Cys(188) can also be prenylated. Analysis of acylation-deficient mutants revealed that lipidation of Cys(188) is essential for proper membrane binding of Cdc42-palm as well as for Cdc42-mediated regulation of gene transcription and induction of densely packed filopodia in neuroblastoma cells. We also found that Cdc42-prenyl is a dominant splice variant in a wide range of commonly used cell lines as well as in the cerebellum, whereas Cdc42-palm is the main Cdc42 isoform in hippocampus, where it is critically involved in the formation of dendritic filopodia and spines. Replacement of endogenous Cdc42 by its acylation-deficient mutants revealed the importance of Cdc42-palm lipidation for its morphogenic and synaptogenic effects in neurons. These findings demonstrate that dual lipidation of Cdc42-palm represents an important regulator of morphogenic signalling in hippocampal neurons.

Molecular Substrates of Altered Axonal Growth and Brain Connectivity in a Mouse Model of Schizophrenia

“…Cdc42Palm is palmitoylated, whereas the canonical form is not (Nishimura et al, 2013; Kang et al, 2008). Wirth et al (2013) reported that the expression level of Cdc42Palm in the hippocampus was approximately 2-fold higher than that of isoform 1. We specifically examined the involvement of Cdc42Palm in axonal growth.…”

Slippery signaling: Palmitoylation-dependent control of neuronal kinase localization and activity

“…For example, the ‘upstream’ proteins that regulate PAK/LIMK1 activity in spines are not known, but it is striking that palmitoylated forms of both Rac and Cdc42, small GTPases that are well known regulators of LIMK1 signaling, are detected in neurons (Kang et al, 2008, Wirth et al, 2013). Moreover, a palmitoylated form of Cdc42 is dominantly expressed in hippocampus (compared to the prenylated form, which is dominant in most other tissues), is preferentially targeted to dendritic spines, and is important for the control of spine morphology (Wirth et al, 2013, Kang et al, 2008). These findings raise the possibility that palmitoylation controls the spine localization and activity of multiple elements of the Rac/Cdc42-PAK-LIMK1 signaling module (Figure 2).…”

Rho signaling: An historical and evolutionary perspective

“…Cdc42 alternative splicing has long remained neglected until recent works showed striking differences in the ability of the two isoforms to induce filopodia (Wirth et al, 2013). The ubiquitous Cdc42 isoform is prenylated, whereas the alternative isoform is brain specific and can be palmitoylated thanks to the cysteine doublet of the CAAx box.…”