Myeloid cell surface antigen CD33 (Sialic acid-binding Ig-like lectin 3) (Siglec-3) (gp67) (CD antigen CD33)
1_MPLLL 6_ LLPLL 11_ WAGAL 16_ AMDPN 21_ FWLQV 26_ QESVT 31_ VQEGL 36_ CVLVP 41_ CTFFH 46_ PIPYY 51_ DKNSP 56_ VHGYW 61_ FREGA 66_ IISRD 71_ SPVAT 76_ NKLDQ 81_ EVQEE 86_ TQGRF 91_ RLLGD 96_ PSRNN 101_ CSLSI 106_ VDARR 111_ RDNGS 116_ YFFRM 121_ ERGST 126_ KYSYK 131_ SPQLS 136_ VHVTD 141_ LTHRP 146_ KILIP 151_ GTLEP 156_ GHSKN 161_ LTCSV 166_ SWACE 171_ QGTPP 176_ IFSWL 181_ SAAPT 186_ SLGPR 191_ TTHSS 196_ VLIIT 201_ PRPQD 206_ HGTNL 211_ TCQVK 216_ FAGAG 221_ VTTER 226_ TIQLN 231_ VTYVP 236_ QNPTT 241_ GIFPG 246_ DGSGK 251_ QETRA 256_ GVVHG 261_ AIGGA 266_ GVTAL 271_ LALCL 276_ CLIFF 281_ IVKTH 286_ RRKAA 291_ RTAVG 296_ RNDTH 301_ PTTGS 306_ ASPKH 311_ QKKSK 316_ LHGPT 321_ ETSSC 326_ SGAAP 331_ TVEMD 336_ EELHY 341_ ASLNF 346_ HGMNP 351_ SKDTS 356_TEYSE
1: Sialic-acid-binding immunoglobulin-like lectin (Siglec) that plays a role in mediating cell-cell interactions and in maintaining immune cells in a resting state (PubMed:10611343, PubMed:11320212, PubMed:15597323). Preferentially recognizes and binds alpha-2,3- and more avidly alpha-2,6-linked sialic acid-bearing glycans (PubMed:7718872). Upon engagement of ligands such as C1q or syalylated glycoproteins, two immunoreceptor tyrosine-based inhibitory motifs (ITIMs) located in CD33 cytoplasmic tail are phosphorylated by Src-like kinases such as LCK (PubMed:10887109, PubMed:28325905). These phosphorylations provide docking sites for the recruitment and activation of protein-tyrosine phosphatases PTPN6/SHP-1 and PTPN11/SHP-2 (PubMed:10206955, PubMed:10556798, PubMed:10887109). In turn, these phosphatases regulate downstream pathways through dephosphorylation of signaling molecules (PubMed:10206955, PubMed:10887109). One of the repressive effect of CD33 on monocyte activation requires phosphoinositide 3-kinase/PI3K (PubMed:15597323)