H. Setiadi et al., RESIDUES THROUGHOUT THE CYTOPLASMIC DOMAIN AFFECT THE INTERNALIZATIONEFFICIENCY OF P-SELECTIN, The Journal of biological chemistry, 270(45), 1995, pp. 26818-26826
The cytoplasmic domains of many membrane proteins have short sequences
, usually including a tyrosine or a di-leucine, that function as sorti
ng signals, P-selectin is an adhesion receptor for leukocytes that is
expressed on activated platelets and endothelial cells, Its 35 residue
cytoplasmic domain contains signals for sorting into regulated secret
ory granules, for endocytosis, and for movement from endosomes to lyso
somes, The domain has a membrane-distal sequence, YGVFTNAAF, that rese
mbles some tyrosine-based signals, We studied the effects of deletions
and mutations in the cytoplasmic tail of human P-selectin on its inte
rnalization in clathrin-coated pits of transfected Chinese hamster ova
ry cells. Mutations and deletions in the putative tyrosine-based motif
did not clearly implicate these residues as critical components of a
short internalization signal, Indeed, a construct containing a truncat
ed 18-residue cytoplasmic domain with a single substitution (K761A/H77
3Stop) was internalized nearly three times as fast as wild-type P-sele
ctin; this construct contained no di-leucine, tyrosine, or other known
sorting motif, Substitution of residues throughout the cytoplasmic do
main affected the internalization rate of P-selectin, Furthermore, the
cytoplasmic domain of P-selectin mediated faster internalization when
attached to the extracellular and transmembrane domains of the low de
nsity lipoprotein receptor than when attached to the corresponding dom
ains of P-selectin. Thus, we were unable to identify a short internali
zation signal in the cytoplasmic tail of P-selectin, Residues througho
ut the cytoplasmic domain, and perhaps the transmembrane sequence to w
hich the domain is attached, affect the efficiency of internalization.