Role of the S-typhimurium actin-binding protein SipA in bacterial internalization

Entry of the bacterium Salmonella typhimurium into host cells, requires mem brane ruffling and rearrangement of the actin cytoskeleton. Here, it is sho wn that the bacterial protein SipA plays a critical role in this process. S ipA binds directly to actin, decreases its critical concentration, and inhi bits depolymerization of actin filaments, These activities result in the sp atial localization and more pronounced outward extension of the Salmonella- induced membrane ruffles, thereby facilitating bacterial uptake.