1 ▁re ceptor ▁transm its ▁signal ing ▁to ▁adjacent ▁surface ▁mole cules , ▁known ▁as ▁P lex ins ; ▁this ▁is ▁necessary ▁because ▁the ▁N pn 1 ▁re ceptor ▁la cks ▁an ▁int rac ell ular ▁domain . ▁The ▁int rac ell ular ▁signal ing ▁medi ated ▁through ▁Sem ap hor ins ▁results ▁in ▁growth ▁cone ▁collapse , ▁guidance , ▁and ▁turning ; ▁this ▁int rac ell ular ▁signal ing ▁is ▁trans du ced ▁through ▁R ho ▁family ▁G TP ases , ▁which ▁act ▁to ▁rem odel ▁the ▁c yt os ke leton ▁of ▁the ▁cell . ▁In ▁addition , ▁several ▁other ▁cell ▁surface ▁mole cules ▁have ▁been ▁shown ▁to ▁interact ▁with ▁secret ed ▁Sem ap hor ins . ▁One ▁example ▁is ▁the ▁Ig ▁cell - ad hes ion ▁mole c ule ▁( Ig C AM ) ▁family ; ▁this ▁family ▁of ▁ad hes ion ▁mole cules ▁are ▁suggested ▁to ▁interact ▁with ▁Sem ap hor ins ▁to ▁fine ▁t une ▁their ▁ax onal ▁pro jections ▁and ▁target ing . ▁The ▁mult itude ▁of ▁mole cules ▁that ▁complex ▁with ▁Sem ap hor ins ▁may ▁be ▁the ▁result ▁of ▁the ▁u bi quit ous ▁nature ▁of ▁Sem ap hor in ▁expression ▁in ▁verte br ates . ▁ ▁During ▁emb ry onic ▁ne uro development , ▁syn ap se ▁elim ination ▁and ▁ax onal ▁pr uning ▁are ▁critical ▁to ▁ensure ▁normal ▁function ing ▁of ▁the ▁central ▁and ▁peri pher al ▁nerv ous ▁system . ▁Studies ▁have ▁suggested ▁that ▁S ema 3 A / Ne urop il