Adenomatous polyposis coli

APC
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 1DEB, 1EMU, 1JPP, 1M5I, 1T08, 1TH1, 1V18, 2RQU, 3AU3, 3NMW, 3NMX, 3NMZ, 3QHE, 3RL7, 3RL8, 3T7U, 4G69, 4YJL, 4YK6, 4YJE
Identifiers
Aliases	APC, BTPS2, DP2, DP2.5, DP3, GS, PPP1R46, adenomatous polyposis coli, WNT signaling pathway regulator
External IDs	MGI: 88039 HomoloGene: 30950 GeneCards: APC
Gene ontology Molecular function • gamma-catenin binding • protein kinase binding • microtubule plus-end binding • microtubule binding • cadherin binding • protein kinase regulator activity • protein binding • beta-catenin binding Cellular component • cytoskeleton • adherens junction • beta-catenin destruction complex • nucleoplasm • cytoplasm • cell projection • cytosol • catenin complex • cell junction • nucleus • lamellipodium • cytoplasmic microtubule • membrane • Wnt signalosome • centrosome • cell-cell adherens junction • microtubule • kinetochore • bicellular tight junction • ruffle membrane • plasma membrane • lateral plasma membrane Biological process • negative regulation of cell proliferation • negative regulation of cyclin-dependent protein serine/threonine kinase activity • mitotic spindle assembly checkpoint • positive regulation of cell migration • positive regulation of protein catabolic process • bicellular tight junction assembly • cellular component disassembly involved in execution phase of apoptosis • regulation of microtubule-based process • cell cycle arrest • positive regulation of pseudopodium assembly • regulation of attachment of spindle microtubules to kinetochore • regulation of cell differentiation • cellular response to DNA damage stimulus • protein complex assembly • pattern specification process • negative regulation of Wnt signaling pathway • cell fate specification • cell adhesion • mitotic cytokinesis • negative regulation of microtubule depolymerization • positive regulation of apoptotic process • canonical Wnt signaling pathway • cell migration • proteasome-mediated ubiquitin-dependent protein catabolic process • beta-catenin destruction complex assembly • beta-catenin destruction complex disassembly • negative regulation of canonical Wnt signaling pathway • Wnt signaling pathway Sources:Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	324	11789
Ensembl	ENSG00000134982	ENSMUSG00000005871
UniProt	P25054	Q61315
RefSeq (mRNA)	NM_001127511 NM_000038 NM_001127510	NM_007462
RefSeq (protein)	NP_000029.2 NP_001120982.1	n/a
Location (UCSC)	Chr 5: 112.71 – 112.85 Mb	Chr 18: 34.22 – 34.32 Mb
PubMed search	[1]	[2]
Wikidata

This article refers to the tumor suppressor APC, in which mutations lead to colon cancer. For the cell-cycle regulatory complex, APC/C, see Anaphase-promoting complex.

Adenomatous polyposis coli (APC) also known as deleted in polyposis 2.5 (DP2.5) is a protein that in humans is encoded by the APC gene.^[3] The APC protein is a negative regulator that controls beta-catenin concentrations and interacts with E-cadherin, which are involved in cell adhesion. Mutations in the APC gene may result in colorectal cancer.^[4]

APC is classified as a tumor suppressor gene. Tumor suppressor genes prevent the uncontrolled growth of cells that may result in cancerous tumors. The protein made by the APC gene plays a critical role in several cellular processes that determine whether a cell may develop into a tumor. The APC protein helps control how often a cell divides, how it attaches to other cells within a tissue, how the cell polarizes and the morphogenesis of the 3D structures,^[5] or whether a cell moves within or away from a tissue. This protein also helps ensure that the chromosome number in cells produced through cell division is correct. The APC protein accomplishes these tasks mainly through association with other proteins, especially those that are involved in cell attachment and signaling. The activity of one protein in particular, beta-catenin, is controlled by the APC protein (see: Wnt signaling pathway). Regulation of beta-catenin prevents genes that stimulate cell division from being turned on too often and prevents cell overgrowth.

The human APC gene is located on the long (q) arm of chromosome 5 in band q22.2 (5q22.2). The APC gene has been shown to contain an internal ribosome entry site. APC orthologs^[6] have also been identified in all mammals for which complete genome data are available.

Structure

The full-length human protein comprises 2,843 amino acids with a (predicted) molecular mass of 311646 Da. Several N-terminal domains have been structurally elucidated in unique atomistic high-resolution complex structures. Most of the protein is predicted to be intrinsically disordered. It is not known if this large predicted unstructured region from amino acid 800 to 2843 persists in vivo or would form stabilised complexes - possibly with yet unidentified interacting proteins.^[7] Recently, it has been experimentally confirmed that the mutation cluster region around the center of APC is intrinsically disordered in vitro.^[8]

Role in cancer

The most common mutation in colon cancer is inactivation of APC. When APC does not have an inactivating mutation, frequently there are activating mutations in beta catenin. Mutations in APC can be inherited, or arise sporadically in the somatic cells, often as the result of mutations in other genes that result in the inability to repair mutations in the DNA. In order for cancer to develop, both alleles (copies of the APC gene) must be mutated. Mutations in APC or β-catenin must be followed by other mutations to become cancerous; however, in carriers of an APC inactivating mutations, the risk of colorectal cancer by age 40 is almost 100%.^[4]

Familial adenomatous polyposis (FAP) is caused by an inherited, inactivating mutation in the APC gene. More than 800 mutations in the APC gene have been identified in families with classic and attenuated types of familial adenomatous polyposis. Most of these mutations cause the production of an APC protein that is abnormally short and presumably nonfunctional. This short protein cannot suppress the cellular overgrowth that leads to the formation of polyps, which can become cancerous. The most common mutation in familial adenomatous polyposis is a deletion of five bases in the APC gene. This mutation changes the sequence of amino acids in the resulting APC protein beginning at position 1309.

Another mutation is carried by approximately 6 percent of people of Ashkenazi (eastern and central European) Jewish heritage. This mutation results in the substitution of the amino acid lysine for isoleucine at position 1307 in the APC protein (also written as I1307K or Ile1307Lys). This change was initially thought to be harmless, but has recently been shown to be associated with a 10 to 20 percent increased risk of colon cancer.

Regulation of proliferation

The (Adenomatous Polyposis Coli) APC protein normally builds a "destruction complex" with glycogen synthase kinase 3-alpha and or beta (GSK-3α/β) and axin via interactions with the 20 AA and SAMP repeats. This complex is then able to bind β-catenins in the cytoplasm, that have dissociated from adherens contacts between cells. With the help of casein kinase 1 (CK1), which carries out an initial phosphorylation of β-catenin, GSK-3β is able to phosphorylate β-catenin a second time. This targets β-catenin for ubiquitination and degradation by cellular proteasomes. This prevents it from translocating into the nucleus, where it acts as a transcription factor for proliferation genes. APC is also thought to be targeted to microtubules via the PDZ binding domain, stabilizing them. The deactivation of the APC protein can take place after certain chain reactions in the cytoplasm are started, e.g. through the Wnt signals that destroy the conformation of the complex. In the nucleus it complexes with legless/BCL9, TCF, and Pygo.

The ability of APC to bind β-catenin has been classically considered to be an integral part of the protein's mechanistic function in the destruction complex, along with binding to Axin through the SAMP repeats.^[9] These models have been substantiated by observations that common APC loss of function mutations in the mutation cluster region often remove several β-catenin binding sites and SAMP repeats. However, recent evidence from Yamulla and colleagues have directly tested those models and imply that APC's core mechanistic functions may not require direct binding to β-catenin, but necessitate interactions with Axin.^[10] The researchers hypothesized that APC's many β-catenin binding site increase the protein's efficiency at destroying β-catenin, yet are not absolutely necessary for the protein's mechanistic function. Further research is clearly necessary to elucidate the precise mechanistic function of APC in the destruction complex.

Mutations

Familial Adenomatous Polyposis of the intestine

Mutations in APC often occur early on in cancers such as colon cancer.^[7] Patients with familial adenomatous polyposis (FAP) have germline mutations, with 95% being nonsense/frameshift mutations leading to premature stop codons. 33% of mutations occur between amino acids 1061-1309. In somatic mutations, over 60% occur within a mutation cluster region (1286-1513), causing loss of axin binding sites in all but 1 of the 20AA repeats. Mutations in APC lead to loss of β-catenin regulation, altered cell migration and chromosome instability.

Neurological role

Rosenberg et al. found that APC directs cholinergic synapse assembly between neurons, a finding with implications for autonomic neuropathies, for Alzheimer's disease, for age-related hearing loss, and for some forms of epilepsy and schizophrenia.^{[11] (29)}

Interactions

APC (gene) has been shown to interact with:

Overview of signal transduction pathways involved in apoptosis.

See also

• MUTYH

References

Further reading

External links

• GeneReviews/NCBI/NIH/UW entry on APC-Associated Polyposis Conditions
• OMIM entries on APC-Associated Polyposis Conditions
• Adenomatous Polyposis Coli Protein at the US National Library of Medicine Medical Subject Headings (MeSH)
• GeneCard
• Database concerning peer-reviewed reports on cancer critical alteration in several genes including (APC (protein)), (TP53), (β-catenin)

PDB gallery
1deb: CRYSTAL STRUCTURE OF THE N-TERMINAL COILED COIL DOMAIN FROM APC  1m5i: Crystal Structure of the coiled coil region 129-250 of the tumor suppressor gene product APC  1th1: Beta-catenin in complex with a phosphorylated APC 20aa repeat fragment  1v18: THE CRYSTAL STRUCTURE OF BETA-CATENIN ARMADILLO REPEAT COMPLEXED WITH A PHOSPHORYLATED APC 20MER REPEAT.