This family includes proteins such as Arp2/3-interacting proteins (Arpin). Arpin regulates actin polymerization by inhibiting the actin-nucleating activity of the Arp2/3 complex [1]. It induces cell turning by pausing cell migration [2].

1: Inhibitory signalling to the Arp2/3 complex steers cell migration. Dang I, Gorelik R, Sousa-Blin C, Derivery E, Guerin C, Linkner J, Nemethova M, Dumortier JG, Giger FA, Chipysheva TA, Ermilova VD, Vacher S, Campanacci V, Herrada I, Planson AG, Fetics S, Henriot V, David V, Oguievetskaia K, Lakisic G, Pierre F, Steffen A, Boyreau A, Peyrieras N, Rottner K, Zinn-Justin S, Cherfils J, Bieche I, Alexandrova AY, David NB, Small JV, Faix J, Blanchoin L, Gautreau A; Nature. 2013;503:281-284. PMID:24132237

2: The Arp2/3 inhibitory protein arpin induces cell turning by pausing cell migration. Gorelik R, Gautreau A; Cytoskeleton (Hoboken). 2015;72:362-371. PMID:26235381