CD300C molecule | Elisa - Clia - Antibody - Protein

Background

CD300C, also known as immune receptor expressed by myeloid cells 2 (IREM-2), is a member of the CD300 family of immunoreceptors. The CD300 family, also known as the LMIR (leukocyte mono-immunoglobulin-like receptor) family, consists of several proteins that are predominantly expressed on the surface of myeloid and some lymphoid cells. These receptors are involved in the regulation of various immune responses, both activating and inhibitory, contributing to immune homeostasis and protection against pathogens.

CD300C is encoded by the CD300C gene located on chromosome 17q25.1 in humans. This receptor is structurally similar to other members of the CD300 family, particularly CD300A, but it has distinct functional properties that are crucial for modulating immune cell activity.

Protein Structure

CD300C is a type I transmembrane protein with the following structural features:

• Extracellular Domain: The extracellular region of CD300C contains a single immunoglobulin (Ig)-like domain. This Ig-like domain is responsible for ligand recognition and binding, playing a critical role in mediating the receptor's immune functions.
• Transmembrane Region: The transmembrane region anchors CD300C in the cell membrane. It spans the lipid bilayer and is essential for the receptor's proper localization and function.
• Cytoplasmic Tail: Unlike some other CD300 family members that possess immunoreceptor tyrosine-based inhibitory motifs (ITIMs), the cytoplasmic tail of CD300C contains an immunoreceptor tyrosine-based activation motif (ITAM). The ITAM is crucial for transducing activating signals into the cell, promoting immune responses.

Classification and Subtypes

CD300C is part of the CD300 family, which includes both activating and inhibitory receptors. Members of this family are classified based on the presence of ITIMs or ITAMs in their cytoplasmic tails:

• Activating Receptors: These receptors, such as CD300C, contain ITAMs or associate with adaptor proteins that have ITAMs. They deliver activating signals that promote immune cell activation and response to pathogens.
• Inhibitory Receptors: These receptors, such as CD300A, contain ITIMs and deliver inhibitory signals that dampen immune responses and prevent excessive inflammation.

Other notable members of the CD300 family include CD300A, CD300B, CD300D, CD300E, CD300F, and CD300G. Each of these receptors plays a unique role in regulating immune cell functions.

Function and Biological Significance

CD300C is primarily involved in the activation of immune responses. Its functions and biological significance include:

1. Activation of Immune Cells: CD300C delivers activating signals through its ITAM. Upon ligand binding, the ITAM is phosphorylated, leading to the recruitment of signaling molecules such as Syk or ZAP-70. This initiates a cascade of intracellular events that result in the activation of immune cells, including increased cytokine production and enhanced phagocytic activity.
2. Role in Inflammatory Responses: CD300C is expressed on various myeloid cells, including monocytes, macrophages, and dendritic cells. Its activation promotes inflammatory responses, aiding in the clearance of pathogens and infected cells. This is particularly important in the early stages of immune response where rapid activation of innate immunity is crucial.
3. Regulation of Adaptive Immunity: CD300C can influence adaptive immune responses by modulating the activity of dendritic cells. Activated dendritic cells present antigens to T cells, thereby shaping the adaptive immune response. CD300C-mediated activation of dendritic cells can enhance their ability to stimulate T cells.
4. Interaction with Phospholipids: Similar to other CD300 family members, CD300C can bind to phospholipids such as phosphatidylserine and phosphatidylethanolamine. These interactions are important for recognizing apoptotic cells and promoting their clearance, which is essential for resolving inflammation and maintaining tissue homeostasis.
5. Role in Allergic Responses: CD300C is expressed on eosinophils and mast cells, key players in allergic reactions. Its activation can enhance the release of inflammatory mediators, contributing to the pathogenesis of allergic diseases.

Clinical Issues

CD300C is implicated in various clinical conditions, primarily due to its role in immune activation:

1. Autoimmune Diseases: Dysregulation of CD300C expression or function can contribute to autoimmune diseases. Excessive activation of immune cells through CD300C can lead to tissue damage and chronic inflammation, characteristic of autoimmune disorders.
2. Infectious Diseases: CD300C plays a role in the immune response to infections. Its activation can enhance the ability of immune cells to combat pathogens. However, overactivation can also lead to tissue damage and exacerbation of inflammatory responses.
3. Allergic Conditions: Given its expression on eosinophils and mast cells, CD300C is involved in the development and exacerbation of allergic diseases such as asthma and allergic rhinitis. Targeting CD300C-mediated pathways could offer therapeutic potential in managing allergic inflammation.
4. Cancer: The role of CD300C in cancer is complex and context-dependent. While activation of immune responses through CD300C can aid in anti-tumor immunity, chronic activation may also promote a pro-inflammatory environment that supports tumor growth and metastasis.

Summary

CD300C is a crucial activating receptor in the CD300 family, expressed predominantly on myeloid cells. Structurally, it features an extracellular Ig-like domain, a transmembrane region, and a cytoplasmic tail with an ITAM that mediates activating signals. CD300C plays significant roles in activating immune responses, regulating inflammatory processes, and influencing adaptive immunity. Its involvement in various clinical conditions, including autoimmune diseases, infections, allergies, and cancer, underscores its importance in immune regulation. Understanding the precise mechanisms of CD300C's function and its interactions with other immune molecules is essential for developing targeted therapies aimed at modulating immune responses in diverse diseases.