Activates CDC42, a member of the Ras-like family of Rho-and Rac proteins, by exchanging bound GDP for free GTP. Plays a role in regulating the actin cytoskeleton and cell shape. Activates MAPK8.
Expressed in different tissues, including brain, cerebellum, peripheral nerve, skeletal muscle, heart, uterus, placenta and testis.
Charcot-Marie-Tooth disease 4H (CMT4H) [MIM:609311]: A recessive demyelinating form of Charcot-Marie-Tooth disease, a disorder of the peripheral nervous system, characterized by progressive weakness and atrophy, initially of the peroneal muscles and later of the distal muscles of the arms. Charcot-Marie-Tooth disease is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathies (designated CMT1 when they are dominantly inherited) and primary peripheral axonal neuropathies (CMT2). Demyelinating neuropathies are characterized by severely reduced nerve conduction velocities (less than 38 m/sec), segmental demyelination and remyelination with onion bulb formations on nerve biopsy, slowly progressive distal muscle atrophy and weakness, absent deep tendon reflexes, and hollow feet. By convention autosomal recessive forms of demyelinating Charcot-Marie-Tooth disease are designated CMT4. Note=The disease is caused by mutations affecting the gene represented in this entry.
The part of the protein spanning the actin filament-binding domain together with the DH domain and the first PH domain is necessary and sufficient for microspike formation. Activation of MAPK8 requires the presence of all domains with the exception of the actin filament-binding domain.
Cytoplasm > cytoskeleton. Cell projection > filopodium. Concentrated in filopodia and poorly detected at lamellipodia. Binds along the sides of actin fibers.