AMBRA1

AMBRA1 (activating molecule in Beclin1-regulated autophagy)[5][6] is a protein that is able to regulate cancer cells through autophagy.[7] AMBRA1 is described as a mechanism cells use to divide[8] and there is new evidence demonstrating the role and impact of AMBRA1 as a candidate for the treatment of several disorders and diseases, including anticancer therapy. It is known to suppress tumors [9] and plays a role in mitophagy and apoptosis.[10] AMBRA1 can be found in the cytoskeleton and mitochondria and during the process of autophagy, it is localized at the endoplasmic reticulum.[11] In normal conditions, AMBRA1 is dormant and will bind to BCL2 in the outer membrane. This relocation enables autophagosome nucleation.[12] AMBRA1 protein is involved in several cellular processes and is involved in the regulation of the immune system and nervous system.[6]

AMBRA1
Identifiers
AliasesAMBRA1, DCAF3, WDR94, autophagy and beclin 1 regulator 1
External IDsOMIM: 611359 MGI: 2443564 HomoloGene: 18204 GeneCards: AMBRA1
Orthologs
SpeciesHumanMouse
Entrez

55626

228361

Ensembl

ENSG00000110497

ENSMUSG00000040506

UniProt

Q9C0C7

A2AH22

RefSeq (mRNA)

NM_001080754
NM_172669

RefSeq (protein)

NP_001074223
NP_766257

Location (UCSC)Chr 11: 46.4 – 46.59 MbChr 2: 91.56 – 91.75 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Function

AMBRA1 serves to regulate the process of autophagy and this is the cellular breakdown and recycling of unnecessary or damaged cellular components.[10] This protein interacts with other proteins and genes to initiate the formation of autophagosomes, an essential component of autophagy. Cellular processes such as cell proliferation, apoptosis, and cellular metabolism are regulated through the interactions between AMBRA1 and other proteins.[9] AMBRA1 is involved in regulating the cell cycle and it recognizes and binds to D-type cyclins which promotes cell proliferation.[13] This leads to cyclin-D degradation where AMBRA1 suppresses tumors, prevents their growth, and promotes genetic integrity.[12] AMBRA1 is also known to mediate polyubiquitylation of several proteins.[12] Bartolomeo et al. demonstrated AMBRA1 signals the motor complex to initiate autophagy when it is released from microtubules.[14] Through autophagy, cellular homeostasis is maintained, and the buildup of toxic or damaged proteins is prevented. Reynolds(2021) shows the repercussions of the loss of AMBRA1, which can no longer control the cell cycle from uncontrolled cell division and growth.[7] One of the interactions AMBRA1 has with Beclin1 aids in cell proliferation and protein replacement during neural development.[15] AMBRA1 is able to promote activity in PIK3C3, increase kinase activity during autophagy, and activate ULK1.[9] AMBRA1 promotes FOXO3 and Nazio et al. (2021) showed when AMBRA1 is reduced, there is inhibition of STAT3 signaling which reduces the regulation of innate and adaptive immunity.[12] In addition, AMBRA1 is an essential component for STAT3 signaling as FOXO3 regulates gene expression in autophagy.[12]

Mechanism

The exact mechanisms of this protein are not yet fully understood. Several processes including autophagy and apoptosis are some that AMBRA1 is involved with.[10] Through the formation of autophagosomes, structures that engulf cellular components to break them down,[16] autophagy is initiated. AMBRA1 regulates the activity of the mTORC1 complex and this complex serves as a regulator of cell metabolism and growth.[10] Apart from autophagy, AMBRA1 plays an essential role in apoptosis and cell proliferation. For enabling cell death, the p53 pathway is activated and this is done upon the release of cytochrome C from mitochondria.[17] AMBRA1 has been a topic of research for anti-cancer therapies through the regulation of the immune system.[10] AMBRA1 is additionally involved in the development of the nervous system through the regulation of biological processes involving Parkinson's disease and other neurodegenerative disorders.[9]

Interactions

Simoneschi et al.[14] demonstrated that there is an interaction between AMBRA1 and the cyclin-D pathway. D-type cyclins activate CDK4 and CDK6 and AMBRA1 protein targets these cyclins for degradation. The decrease in AMBRA1 proteins showed the prevention of polyubiquitylation of cyclin D1.[14] The interactions provide evidence that AMBRA1 plays a role in the regulation of different cellular processes such as autophagy, cell proliferation, apoptosis, and metabolism. AMBRA1 interacts with Beclin1 and ULK1 to initiate autophagy and form autophagosomes.[15] The interaction with ULK1 also regulates cell proliferation.[15] AMBRA1 interacts with Bcl2 and mito-and this aids in regulating and promoting apoptosis.[18] There is a correlation between apoptosis and autophagy where AMBRA1 is released from Bcl2 when autophagy takes place.[15] This process increases Beclin1 activity and Strappazzon et al. found that the interactions are reduced during apoptosis.[15] When AMBRA1 interacts with DLC1, a complex associated with cell division, the complex is moved to the endoplasmic reticulum[14] and the complex is harnessed to the cytoskeleton.[10] AMBRA1 also interacts with the protein phosphatase 2A (PPP2CA) and this promotes MYC dephosphorylation and degradation.[9] MYC is an oncogene and when degraded, it results in tumor suppression.[19] The interactions with AMBRA1 and other proteins suggest the importance of AMBRA1 in cellular processes.

Clinical significance

AMBRA1 is clinically significant due to the importance of this protein in cellular processes such as apoptosis and cell proliferation. Diseases such as cancer,[10] neurodegenerative disorders and autoimmune diseases can arise. Frias et al., through studies concluded that the deletion of AMBRA1 results in the inhibition of tumors and melanoma and reduced cytokine-mediated signaling.[20] Tumorigenisis and tumor proliferation takes place when AMBRA1 interacts with and induces several proteins including cyclin D.[10] Diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease contain autophagy alterations.[21] AMBRA1 plays a role in the development of Parkinson's disease and in interacting with Parkin, an E3 ubiquitin ligase, there is inhibition of Parkin mitophagy.[20] AMBRA1 is involved in the regulation of the immune system and upcoming research demonstrates this protein might play a role in the development of autoimmune diseases since AMBRA1 is involved in autophagy.[15] Understanding the functions of AMBRA1 and the role it plays in disease pathogenesis provide insight into the development of new treatment and therapies for the listed disorders.

References

  1. GRCh38: Ensembl release 89: ENSG00000110497 - Ensembl, May 2017
  2. GRCm38: Ensembl release 89: ENSMUSG00000040506 - Ensembl, May 2017
  3. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. Schoenherr C, Byron A, Griffith B, Loftus A, Wills JC, Munro AF, et al. (August 2020). "The autophagy protein Ambra1 regulates gene expression by supporting novel transcriptional complexes". The Journal of Biological Chemistry. 295 (34): 12045–12057. doi:10.1074/jbc.ra120.012565. PMC 7443501. PMID 32616651.
  6. Nazio F, Po A, Abballe L, Ballabio C, Diomedi Camassei F, Bordi M, et al. (September 2021). "Targeting cancer stem cells in medulloblastoma by inhibiting AMBRA1 dual function in autophagy and STAT3 signalling". Acta Neuropathologica. 142 (3): 537–564. doi:10.1007/s00401-021-02347-7. PMC 8357694. PMID 34302498.
  7. Li X, Lyu Y, Li J, Wang X (2022). "AMBRA1 and its role as a target for anticancer therapy". Frontiers in Oncology. 12: 946086. doi:10.3389/fonc.2022.946086. PMC 9551033. PMID 36237336.
  8. "AMBRA1 Protein Found to Be an Important Tumor Suppressor - NCI". www.cancer.gov. 2021-05-14. Retrieved 2023-05-09.
  9. "AMBRA1 Protein Found to Be an Important Tumor Suppressor". NCI. 14 May 2021.
  10. Schoenherr C, Byron A, Griffith B, Loftus A, Wills JC, Munro AF, et al. (August 2020). "The autophagy protein Ambra1 regulates gene expression by supporting novel transcriptional complexes". The Journal of Biological Chemistry. 295 (34): 12045–12057. doi:10.1074/jbc.RA120.012565. PMC 7443501. PMID 32616651.
  11. "UniProt". www.uniprot.org. Retrieved 2023-05-09.
  12. "AMRA1_HUMAN". UniProt. Q9C0C7.
  13. Simoneschi D, Rona G, Zhou N, Jeong YT, Jiang S, Milletti G, et al. (April 2021). "CRL4AMBRA1 is a master regulator of D-type cyclins". Nature. 592 (7856): 789–793. Bibcode:2021Natur.592..789S. doi:10.1038/s41586-021-03445-y. PMC 8875297. PMID 33854235.
  14. Simoneschi D, Rona G, Zhou N, Jeong YT, Jiang S, Milletti G, et al. (April 2021). "CRL4AMBRA1 is a master regulator of D-type cyclins". Nature. 592 (7856): 789–793. Bibcode:2021Natur.592..789S. doi:10.1038/s41586-021-03445-y. PMC 8875297. PMID 33854235.
  15. Di Bartolomeo S, Corazzari M, Nazio F, Oliverio S, Lisi G, Antonioli M, et al. (October 2010). "The dynamic interaction of AMBRA1 with the dynein motor complex regulates mammalian autophagy". The Journal of Cell Biology. 191 (1): 155–168. doi:10.1083/jcb.201002100. PMC 2953445. PMID 20921139.
  16. "Autophagosome", Wikipedia, 2022-11-14, retrieved 2023-05-10
  17. Strappazzon F, Di Rita A, Cianfanelli V, D'Orazio M, Nazio F, Fimia GM, Cecconi F (June 2016). "Prosurvival AMBRA1 turns into a proapoptotic BH3-like protein during mitochondrial apoptosis". Autophagy. 12 (6): 963–975. doi:10.1080/15548627.2016.1164359. PMC 4922440. PMID 27123694.
  18. Strappazzon F, Vietri-Rudan M, Campello S, Nazio F, Florenzano F, Fimia GM, et al. (April 2011). "Mitochondrial BCL-2 inhibits AMBRA1-induced autophagy". The EMBO Journal. 30 (7): 1195–1208. doi:10.1038/emboj.2011.49. PMC 3094111. PMID 21358617.
  19. Dingar D, Tu WB, Resetca D, Lourenco C, Tamachi A, De Melo J, et al. (August 2018). "MYC dephosphorylation by the PP1/PNUTS phosphatase complex regulates chromatin binding and protein stability". Nature Communications. 9 (1): 3502. Bibcode:2018NatCo...9.3502D. doi:10.1038/s41467-018-05660-0. PMC 6115416. PMID 30158517.
  20. Frias A, Di Leo L, Antoranz A, Nazerai L, Carretta M, Bodemeyer V, et al. (March 2023). "Ambra1 modulates the tumor immune microenvironment and response to PD-1 blockade in melanoma". Journal for Immunotherapy of Cancer. 11 (3): e006389. doi:10.1136/jitc-2022-006389. PMC 9990656. PMID 36868570.
  21. Van Humbeeck C, Cornelissen T, Hofkens H, Mandemakers W, Gevaert K, De Strooper B, Vandenberghe W (July 2011). "Parkin interacts with Ambra1 to induce mitophagy". The Journal of Neuroscience. 31 (28): 10249–10261. doi:10.1523/JNEUROSCI.1917-11.2011. PMC 6623066. PMID 21753002.
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