CD33 Human

CD33 Human Recombinant

Recombinant human CD33, produced in E. coli, is a single, non-glycosylated polypeptide chain. It comprises 265 amino acids (specifically, amino acids 18-259) and has a molecular weight of 29.1 kDa. The CD33 protein is fused to a 23 amino acid His-tag at its N-terminus and is purified using proprietary chromatographic techniques.
Shipped with Ice Packs
Cat. No.
BT28269
Source
Escherichia Coli.
Appearance
Clear, sterile filtered solution.

CD33 Human, Sf9

CD33 Human Recombinant, Sf9

CD33, a single-pass type I transmembrane protein, is produced in Sf9 insect cells using baculovirus expression system. This recombinant protein encompasses amino acids 18 to 259 of the extracellular domain of human CD33, fused to a C-terminal His-tag and a human IgG-Fc domain. The resulting protein has a total of 484 amino acids and a molecular weight of approximately 54 kDa. SDS-PAGE analysis under reducing conditions reveals multiple bands within the 50-70 kDa range, likely representing glycosylated forms of the protein. The purification process involves proprietary chromatographic methods to ensure high purity.
Shipped with Ice Packs
Cat. No.
BT28391
Source
Sf9, Baculovirus cells.
Appearance
Clear, colorless solution, sterile-filtered.
Definition and Classification

CD33, also known as Siglec-3 (sialic acid-binding immunoglobulin-like lectin 3), is a transmembrane receptor primarily expressed on cells of myeloid lineage . It belongs to the SIGLEC family of lectins, which are characterized by their ability to bind sialic acids . CD33 is classified within the immunoglobulin superfamily due to its extracellular portion containing two immunoglobulin domains (one IgV and one IgC2 domain) .

Biological Properties

Key Biological Properties: CD33 is a glycosylated transmembrane protein that plays a role in cell-cell interactions and maintaining immune cells in a resting state . It contains immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in its intracellular portion, which are involved in the inhibition of cellular activity .

Expression Patterns and Tissue Distribution: CD33 is predominantly expressed on myeloid cells, including monocytes, granulocytes, and macrophages . It is also found in the spleen, bone marrow, and blood . Additionally, CD33 expression has been observed in some lymphoid cells .

Biological Functions

Primary Biological Functions: CD33 functions as an inhibitory receptor that downregulates cell activation upon phosphorylation of its ITIM sequence . It plays a crucial role in immune responses by inhibiting phagocytosis and regulating the production of inflammatory cytokines .

Role in Immune Responses and Pathogen Recognition: CD33 is involved in the recognition of sialic acid-modified proteins or lipids, which are common on the surface of pathogens . This recognition helps in the regulation of immune responses and the prevention of excessive inflammation .

Modes of Action

Mechanisms with Other Molecules and Cells: Upon binding to sialic acid residues, the ITIMs of CD33 are phosphorylated, creating docking sites for Src homology 2 (SH2) domain-containing proteins such as SHP-1 and SHP-2 phosphatases . This recruitment leads to the inhibition of downstream signaling cascades, ultimately reducing cellular activation .

Binding Partners and Downstream Signaling Cascades: CD33 interacts with various sialic acid-containing ligands, including glycoproteins and glycolipids . The binding of these ligands triggers the phosphorylation of ITIMs and the recruitment of SHP-1 and SHP-2, which inhibit signaling pathways involved in cell activation .

Regulatory Mechanisms

Regulatory Mechanisms Controlling Expression and Activity: The expression and activity of CD33 are regulated by various mechanisms, including transcriptional regulation and post-translational modifications . Suppressor of cytokine signaling 3 (SOCS3) can bind to the phosphorylated ITIM of CD33, leading to its accelerated proteasomal degradation .

Transcriptional Regulation and Post-Translational Modifications: CD33 expression is influenced by cytokines and other signaling molecules that modulate its transcription . Post-translational modifications, such as phosphorylation, play a critical role in regulating CD33 activity and its interactions with other proteins .

Applications

Biomedical Research: CD33 is widely studied in the context of hematological malignancies, particularly acute myeloid leukemia (AML) . It serves as a marker for myeloid cells and is used to study myeloid differentiation and immune regulation .

Diagnostic Tools: CD33 is utilized in diagnostic tools such as flow cytometry and immunohistochemistry to identify and characterize myeloid cells in various diseases .

Therapeutic Strategies: CD33 is a target for immunotherapy in AML, with therapies such as antibody-drug conjugates and chimeric antigen receptor (CAR) T cells being developed to target CD33-expressing cells . These therapies aim to selectively eliminate malignant cells while sparing normal cells .

Role in the Life Cycle

Role Throughout the Life Cycle: CD33 plays a role in the regulation of immune responses throughout the life cycle, from development to aging . It is involved in maintaining immune homeostasis and preventing excessive inflammation . Dysregulation of CD33 expression or function has been implicated in various diseases, including hematological malignancies and neurodegenerative disorders .

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