Abstract
Eukaryotic cells extend a variety of surface protrusions to direct cell motility. Formation of protrusions is mediated by coordinated actions between the plasma membrane and the underlying actin cytoskeleton. Here, we found that the single calponin homology (CH) domain-containing protein CHDP-1 induces the formation of cell protrusions in C. elegans. CHDP-1 is anchored to the cortex through its amphipathic helix. CHDP-1 associates through its CH domain with the small GTPase Rac1/CED-10, which is a key regulator of the actin cytoskeleton. CHDP-1 preferentially binds to the GTP-bound active form of the CED-10 protein and preserves the membrane localization of GTP-CED-10. Hence, by coupling membrane expansion to Rac1-mediated actin dynamics, CHDP-1 promotes the formation of cellular protrusions in vivo.
Highlights
In eukaryotic cells, the actin cytoskeleton forms a cortical shell around the cell periphery, which allows the plasma membrane to undergo frequent structural changes
We identified that the single calponin homology (CH) domain-containing protein CHDP-1 promotes the formation of cell protrusions in C. elegans
CHDP-1 localizes to the cell cortex and through its calponin homology (CH) domain, CHDP-1 directly binds to the master actin regulator Rac1/CED-10 and enhances the membrane localization of the active CED-10 protein
Summary
The actin cytoskeleton forms a cortical shell around the cell periphery, which allows the plasma membrane to undergo frequent structural changes. The Rho family of small GTPases generally act on membranes and affect the movement of these membranes by changing the membrane-associated actin cytoskeleton. Rac and Cdc induce plasma membrane protrusions, including lamellipodia and filopodia, while RhoA activation stimulates the formation of actin stress fibers [1]. Through the multi-protein WAVE complex, Rac indirectly stimulates the formation of new actin filaments [2,3]. Rac and CDC42 target PAK family members, which in turn phosphorylate LIMKs (LIM domain kinases), and act on the actin-severing factor cofilin [4,5,6]. The activity of Rho GTPases is strictly controlled by various regulatory proteins, including guanine nucleotide exchange factors (GEFs), which convert the inactive GDP-bound enzymes into active GTP-bound forms, and GTPase-activating proteins (GAPs), which stimulate GTP hydrolysis, thereby converting the active GTPases into their inactive forms
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