specific granule membrane

Definition

Target type: cellularcomponent

The lipid bilayer surrounding a specific granule, a granule with a membranous, tubular internal structure, found primarily in mature neutrophil cells. Most are released into the extracellular fluid. Specific granules contain lactoferrin, lysozyme, vitamin B12 binding protein and elastase. [GOC:bf, PMID:7334549]

Specific granules are membrane-bound organelles found in various cell types, particularly in neutrophils, eosinophils, and basophils. They are characterized by their unique content of proteins and enzymes that play crucial roles in the immune response. The membrane of specific granules is a specialized structure that serves as a barrier and facilitates the regulated release of their contents.

**Specific Granule Membrane Composition:**

- **Phospholipids:** Like all cellular membranes, the specific granule membrane is primarily composed of phospholipids, including phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and sphingomyelin. These lipids form a bilayer structure, creating a barrier between the granule interior and the surrounding cytoplasm.
- **Proteins:** The specific granule membrane is enriched in specific proteins that contribute to its structure, function, and interaction with other cellular components. These proteins include:
- **Integrins:** Integrins are transmembrane proteins that mediate cell-cell and cell-matrix interactions. They play a role in adhesion, migration, and signal transduction.
- **Adhesion molecules:** Other adhesion molecules, such as CD11b/CD18 (Mac-1), are present on the specific granule membrane. These molecules facilitate interactions with target cells and contribute to immune responses.
- **Transporters:** Membrane transporters are essential for regulating the movement of ions and small molecules across the granule membrane. Examples include proton pumps and chloride channels.
- **Enzymes:** Some specific granule membranes contain enzymes, such as protein kinases and phosphatases, which regulate signaling pathways and protein phosphorylation.
- **Receptors:** Receptors on the specific granule membrane can bind to specific ligands, triggering signaling cascades and mediating interactions with other cells.

**Function of the Specific Granule Membrane:**

- **Encapsulation and Protection:** The membrane acts as a barrier, separating the granule's content from the cytoplasm and preventing premature release.
- **Targeted Release:** The specific granule membrane plays a crucial role in the regulated release of its contents, known as degranulation. This process is triggered by specific stimuli, such as pathogen-associated molecular patterns (PAMPs) or inflammatory mediators.
- **Signal Transduction:** The membrane serves as a platform for signal transduction events, integrating signals from the extracellular environment and initiating intracellular responses.
- **Cell-Cell Interactions:** Specific granule membrane proteins, such as integrins and adhesion molecules, facilitate interactions with other cells, contributing to immune responses and tissue repair.

**Clinical Significance:**

- **Immune Disorders:** Dysregulation of specific granule membrane function can contribute to immune disorders, including autoimmune diseases and allergies.
- **Infections:** Granule membrane defects can impair the ability of neutrophils and other immune cells to effectively kill pathogens.
- **Cancer:** Specific granule membrane proteins are implicated in cancer development and progression.

In summary, the specific granule membrane is a complex and dynamic structure that plays a critical role in the immune response. Its composition and function are tightly regulated, ensuring the efficient and targeted release of granule contents to combat infections, promote tissue repair, and maintain immune homeostasis.'
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Proteins (48)

Compounds (460)