Table 1.

A list of important short-sequence signal motifs for the internalization and trafficking of membrane receptors and proteins.

Membrane Receptor/Protein	Signal Motifs	Targeted Pathways	Reference
Membrane Receptors:
CD-Mannose-6-phosphate receptor	YKYSKV	Endocytosis/lysosomal targeting	[185]
CI-Mannose-6-phosphate receptor	YSKV	Endocytosis/lysosomal targeting	[136]
Glutamate receptor	YWL	Endocytosis	[146]
GC-A/NPRA	GDAY	Endocytosis	[62]
GC-ANPRA	FQQI	Endocytosis	[26]
Insulin-like growth factor receptor	YxxPhi	Endocytosis	[136, 185]
LDL receptor	FDNPVY	Endocytosis	[145]
LH receptor	GTALL	Endocytosis	[186]
LDL-related receptor	YATL	Endocytosis	[187]
Mannose phosphate receptor	FENTLY	Lysosomal targeting	[136, 185]
Platelet activating factor receptor	[YF]xNPx[YF]	Endocytosis	[188]
Protease-activated receptor-1	YKKL	Endocytosis	[140]
P2X receptor	YEQGL	Endocytosis	[189]
Transferrin receptor	YTRF/Q	Endocytosis	[136, 185]
T-cell receptor	YQPL	Endocytosis	[136]
Membrane Proteins:
Acetylcholine transporter	DSLL	Endosomal targeting	[147]
Beta-amyloid precursor protein	YENPTY	Endocytosis	[190]
CD3 Chains	[DE]xxxL[LI]	Endocytosis	[191]
Integrin	NPxY	Endocytosis	[192]
GLUT4	FQQI	Endocytosis/lysosomal targeting	[193]

The evidence suggest that various short sequence signal motifs usually contain tyrosine or phenylalanine residues, followed by hydrophobic and/or aromatic residues. Certain sequence motifs also contain acidic residues with required amino acid residue tyrosine. Membrane receptors and proteins also make the use of dileucine short signal motifs. GC-A, guanylyl cyclase-A; NPRA, natriuretic peptide receptor-A; LDL, low density lipoprotein; LH, leutinizing hormone; x, refers to any amino acid residue; P2X receptor, purinergic P2Xreceptor; Phi, refers to hydrophobic amino acid residue; GLUT4, glucose transporter 4.