Leukocyte immunoglobulin-like receptor subfamily A member 5 (LILR-A5) also known as CD85 antigen-like family member F (CD85f), immunoglobulin-like transcript 11 (ILT-11), and leukocyte immunoglobulin-like receptor 9 (LIR-9) is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the ''LILRA5''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. This gene is one of the leukocyte receptor genes that form a gene cluster on the chromosomal region 19q13.4. Four alternatively spliced

transcript variants Alternative splicing, alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to produce different splice variants. For example, some exons of a gene may be included ...

encoding distinct

isoforms A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene and are the result of genetic differences. While many perform the same or similar biological roles, some isoforms have uniqu ...

have been described.

Function

The function of LILRA5 is currently unknown. However, it is highly homologous to other LILR genes, thus it is assumed to have similar functions to other LIR family members, i.e. activating and inhibitory functions in

leukocytes White blood cells (scientific name leukocytes), also called immune cells or immunocytes, are cells of the immune system that are involved in protecting the body against both infectious disease and foreign entities. White blood cells are genera ...

. Crosslink of this receptor protein on the surface of

monocyte Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and monocyte-derived dendritic cells. As a part of the vertebrate innate immune system monocytes also ...

s has been shown to induce

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

flux and secretion of several

proinflammatory cytokines An inflammatory cytokine or proinflammatory cytokine is a type of signaling molecule (a cytokine) that is secreted from immune cells like helper T cells (Th) and macrophages, and certain other cell types that promote inflammation. They include int ...

, which suggests the roles of this protein in triggering innate immune responses.

Clinical significance

A recent genome-wide association study (GWAS) has found that genetic variations in ''LILRA5'' are associated with late-onset sporadic Alzheimer’s disease (LOAD). LILBR2 plays a critical role in the inhibition of axonal regeneration and functional recovery after

brain injury Brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating trauma-induced damage. A common ...

. However, recent studies demonstrate that LILRB2 is a

β-Amyloid Amyloid beta (Aβ, Abeta or beta-amyloid) denotes peptides of 36–43 amino acids that are the main component of the amyloid plaques found in the brains of people with Alzheimer's disease. The peptides derive from the amyloid-beta precursor prot ...

receptor and may contribute to synaptic loss and

cognitive impairment Cognitive impairment is an inclusive term to describe any characteristic that acts as a barrier to the cognition process or different areas of cognition. Cognition, also known as cognitive function, refers to the mental processes of how a person ...

Alzheimer's disease Alzheimer's disease (AD) is a neurodegenerative disease and the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As the disease advances, symptoms can include problems wit ...

. Due to its proximity to LILRB2, it is believed that LILRA5 mutation may also contribute to Alzheimer's disease.

References

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