The Actin Nucleation and Polymerization Antibody Sampler Kit provides an economical means to evaluate the presence and status of actin nucleation and polymerization. The kit contains enough primary antibody to perform two western blots per primary.

Actin nucleation is the process of forming new actin filaments and is necessary to stimulate actin polymerization. Actin polymerization is vital for cell motility, cell division, and cell adhesion. Rac and Cdc42, members of the Rho-GTPase family, play key roles in actin dynamics, membrane trafficking, transcriptional regulation, cell growth, and development (1). GTP binding stimulates the activity of Rac/Cdc42, and the hydrolysis of GTP to GDP through the intrinsic GTPase activity or Rac/Cdc42, rendering it inactive. GTP hydrolysis is aided by GTPase activating proteins (GAPs), while exchange of GDP for GTP is facilitated by guanine nucleotide exchange factors (GEFs). Another level of regulation is achieved through binding of RhoGDI, a guanine dissociation inhibitor, which retains Rho family GTPases, including Rac and Cdc42, in their inactive GDP-bound state (2,3). Hematopoietic WASP and ubiquitously expressed N-WASP are autoinhibited in unstimulated cells. Upon stimulation they are activated by Cdc42, which relieves the autoinhibition in conjunction with phosphatidyl inositol 4,5-bisphosphate (4). Three WAVE (Wasf, SCAR) family proteins are similar in sequence to WASP and N-WASP, but lack the WASP/N-WASP autoinhibition domains and are indirectly activated by Rac (4). WAVE-2 is widely distributed, while WAVE-1 and WAVE-3 are strongly expressed in the brain (5). The highly conserved ARP2/3 complex is an important actin nucleation protein complex consisting of ARP2, ARP3, and ARPC1-5. The ARP2/3 complex promotes branching of existing actin filaments and formation of daughter filaments following activation by nucleation-promoting factors, such as WASP/WAVE or cortactin (6). Profilins are conserved actin binding proteins that affect the rate of actin polymerization by binding actin monomers and promoting exchange of ADP for ATP (reviewed in 7). Profilins bind to proteins involved in the regulation of actin dynamics including paladin (8), dynamin-I (9), VASP (10), and N-WASP (11).