CD33

The extracellular portion of this receptor contains two immunoglobulin domains (one IgV and one IgC2 domain), placing CD33 within the immunoglobulin superfamily. The intracellular portion of CD33 contains immunoreceptor tyrosine-based inhibitory motifs (ITIMs) that are implicated in inhibition of cellular activity.[http://www.ebi.uniprot.org/uniprot-srv/uniProtView.do?proteinAc=P20138 Myeloid cell surface antigen CD33 precursor – Homo sapiens (Human)]

CD33 can be stimulated by any molecule with sialic acid residues such as glycoproteins or glycolipids. Upon binding, the immunoreceptor tyrosine-based inhibition motif (ITIM) of CD33, present on the cytosolic portion of the protein, is phosphorylated and acts as a docking site for Src homology 2 (SH2) domain-containing proteins like SHP phosphatases. This results in a cascade that inhibits phagocytosis in the cell.{{cite journal | vauthors = Zhao L | title = CD33 in Alzheimer's Disease - Biology, Pathogenesis, and Therapeutics: A Mini-Review | journal = Gerontology | volume = 65 | issue = 4 | pages = 323–331 | date = 2018-12-12 | pmid = 30541012 | doi = 10.1159/000492596 | doi-access = free }}

CD33 controls microglial activation but in Alzheimer disease it goes overdrive in presence of amyloid and tau proteins, its expression is known to be tied to TREM2.{{cite journal | vauthors = Griciuc A, Patel S, Federico AN, Choi SH, Innes BJ, Oram MK, Cereghetti G, McGinty D, Anselmo A, Sadreyev RI, Hickman SE, El Khoury J, Colonna M, Tanzi RE | display-authors = 6 | title = TREM2 Acts Downstream of CD33 in Modulating Microglial Pathology in Alzheimer's Disease | journal = Neuron | volume = 103 | issue = 5 | pages = 820–835.e7 | date = September 2019 | pmid = 31301936 | pmc = 6728215 | doi = 10.1016/j.neuron.2019.06.010 }}{{cite journal | vauthors = Chan G, White CC, Winn PA, Cimpean M, Replogle JM, Glick LR, Cuerdon NE, Ryan KJ, Johnson KA, Schneider JA, Bennett DA, Chibnik LB, Sperling RA, Bradshaw EM, De Jager PL | display-authors = 6 | title = CD33 modulates TREM2: convergence of Alzheimer loci | journal = Nature Neuroscience | volume = 18 | issue = 11 | pages = 1556–1558 | date = November 2015 | pmid = 26414614 | doi = 10.1038/nn.4126 | pmc = 4682915 }}{{Cite web |title= Deleting CD33 Benefits Mice—If Their Microglia Express TREM2 | work = ALZFORUM|url=https://www.alzforum.org/news/research-news/deleting-cd33-benefits-mice-if-their-microglia-express-trem2 |access-date=2022-02-17 }}{{Cite news| vauthors = Stetka B |date=2022-01-30 |title=How a hyperactive cell in the brain might trigger Alzheimer's disease|language=en|work=NPR|url=https://www.npr.org/sections/health-shots/2022/01/30/1076166807/how-a-hyperactive-cell-in-the-brain-might-trigger-alzheimers-disease|access-date=2022-02-17}}

CD33 is the target of gemtuzumab ozogamicin (trade name: Mylotarg®; Pfizer/Wyeth-Ayerst Laboratories),{{cite journal | vauthors = Walter RB, Gooley TA, van der Velden VH, Loken MR, van Dongen JJ, Flowers DA, Bernstein ID, Appelbaum FR | display-authors = 6 | title = CD33 expression and P-glycoprotein-mediated drug efflux inversely correlate and predict clinical outcome in patients with acute myeloid leukemia treated with gemtuzumab ozogamicin monotherapy | journal = Blood | volume = 109 | issue = 10 | pages = 4168–4170 | date = May 2007 | pmid = 17227830 | pmc = 1885511 | doi = 10.1182/blood-2006-09-047399 }} an antibody-drug conjugate (ADC) for the treatment of patients with acute myeloid leukemia. The drug is a recombinant, humanized anti-CD33 monoclonal antibody (IgG4 κ antibody hP67.6) covalently attached to the cytotoxic antitumor antibiotic calicheamicin (N-acetyl-γ-calicheamicin) via a bifunctional linker (4-(4-acetylphenoxy)butanoic acid).{{cite web | url = http://adcreview.com/adc-university/adcs-101/cytotoxic-agents/calicheamicin/ | title = Calicheamicin (LL-E33288 antibiotics) | work = ADC Review / Journal of Antibody-drug Conjugates | date = 20 March 2015 }}

Several mechanisms of resistance to gemtuzumab ozogamicin have been elucidated.{{cite journal | vauthors = Molica M, Perrone S, Mazzone C, Niscola P, Cesini L, Abruzzese E, de Fabritiis P | title = CD33 Expression and Gentuzumab Ozogamicin in Acute Myeloid Leukemia: Two Sides of the Same Coin | journal = Cancers | volume = 13 | issue = 13 | pages = 3214 | date = June 2021 | pmid = 34203180 | pmc = 8268215 | doi = 10.3390/cancers13133214 | doi-access = free }}

On September 1, 2017, the FDA approved Pfizer's Mylotarg.{{Cite web|url=https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm574507.htm|archive-url=https://web.archive.org/web/20170903080825/https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm574507.htm|url-status=dead|archive-date=September 3, 2017|title=FDA approves Mylotarg for treatment of acute myeloid leukemia | work = Food and Drug Administration|date=24 March 2020}}

Gemtuzumab ozogamicin was initially approved by the U.S. Food and Drug Administration in 2000. However, during post marketing clinical trials researchers noticed a greater number of deaths in the group of patients who received gemtuzumab ozogamicin compared with those receiving chemotherapy alone. Based on these results, Pfizer voluntarily withdrew gemtuzumab ozogamicin from the market in mid-2010, but was reintroduced to the market in 2017.{{cite web | url = http://adcreview.com/gemtuzumab-ozogamicin-mylotarg/ | title = Gemtuzumab ozogamicin (Mylotarg®) Drug Description | work = ADC Review / Journal of Antibody-drug Conjugates | date = 19 July 2015 }}{{cite web | url = https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm216448.htm | archive-url = https://web.archive.org/web/20100623213248/http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm216448.htm | url-status = dead | archive-date = June 23, 2010 | title = Pfizer Voluntarily Withdraws Cancer Treatment Mylotarg from U.S. Market | work = FDA Press Release | date = 21 June 2010 }}{{Cite web |url= https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm574507.htm|archive-url= https://web.archive.org/web/20170903080825/https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm574507.htm|url-status= dead|archive-date= September 3, 2017|title = FDA approves Mylotarg for treatment of acute myeloid leukemia | website = Food and Drug Administration | date = 24 March 2020 }}

CD33 is also the target in Vadastuximab talirine (SGN-CD33A), a novel antibody-drug conjugate being developed by Seattle Genetics, utilizing this company's ADC technology.{{cite web | url = http://adcreview.com/vadastuximab-talirine-sgn-cd33a-drug-description/ | title = Vadastuximab Talirine (SGN CD33a) Drug Description | work = ADC Review / Journal of Antibody-drug Conjugates | date = 23 November 2015 }}

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• {{UCSC gene info|CD33}}

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{{Clusters of differentiation by lineage}}

{{lectins}}

{{Membrane proteins}}

Category:Lectins

Category:SIGLEC

Category:Alzheimer's disease