▁very ▁active ▁in ▁l am el lip odia , ▁pro tr us ions ▁of ▁the ▁cell ▁memb rane ▁formed ▁by ▁act in ▁polym er ization ▁and ▁t read m illing ▁that ▁prop el ▁the ▁cell ▁along ▁a ▁surface ▁as ▁it ▁migr ates ▁towards ▁some ▁target . ▁ ▁Cort act in ▁acts ▁as ▁a ▁link ▁between ▁ext rac ell ular ▁signals ▁and ▁l am el lip od ial ▁“ ste ering .” ▁When ▁a ▁re ceptor ▁ty ros ine ▁kin ase ▁on ▁the ▁cell ▁memb rane ▁bind s ▁to ▁an ▁ad hes ion ▁site , ▁for ▁example , ▁cort act in ▁will ▁be ▁ph osph ory l ated ▁locally ▁to ▁the ▁area ▁of ▁binding , ▁activ ate ▁and ▁rec ruit ▁Ar p 2 / 3 ▁to ▁the ▁act in ▁cor tex ▁in ▁that ▁region , ▁and ▁thus ▁stim ulate ▁cort ical ▁act in ▁polym er ization ▁and ▁movement ▁of ▁the ▁cell ▁in ▁that ▁direction . ▁Mac roph ages , ▁highly ▁mot ile ▁imm une ▁cells ▁that ▁eng ulf ▁cell ular ▁de br is ▁and ▁path og ens , ▁are ▁prop elled ▁by ▁l am el lip odia ▁and ▁identify / migr ate ▁toward ▁a ▁target ▁via ▁chem ot axis ; ▁thus , ▁cort act in ▁must ▁also ▁be ▁activ ated ▁by ▁re ceptor ▁kin ases ▁that ▁pick ▁up ▁a ▁large ▁variety ▁of ▁chemical ▁signals . ▁ ▁Studies ▁have ▁imp licated ▁cort act in ▁in ▁both ▁cl ath rin - medi ated ▁end oc yt osis ▁and ▁cl ath rin - in dependent ▁end oc