The protein encoded by this gene is 10.4 kDa mitochondrial inner membrane protein with two transmembrane domains at the N- and C-terminals.[5][6] These two domains are arranged such that the N- and C-terminals face outward into the intermembrane space while the rest of the protein loops inside the matrix. Though the N-terminal domain is not necessary to direct the localization of HIGD1A, it is required for the survival of the protein.
HIGD1A primarily functions in mitochondrial homeostasis and, thus, cell survival when under conditions of stress, such as hypoxia and glucose deprivation. For instance, HIGD1A promotes survival of pancreatic α and β cells under stress.[4][5] HIGD1A has also been found in other parts of the brain, heart, liver, and kidney, where it enhances the survival of these organs.[4][7] In macrophages, HIGD1A prevents apoptosis by inhibiting cytochrome C release and caspase activity.[5][6]
HIGD1A is also involved in mitochondrial fusion by regulating OPA1 activity. Its inhibition of the cleavage of OPA1 preserves mitochondrial membrane potential, protects against apoptosis, and maintains ATP levels. Its role in mitochondrial fusion also influences downstream processes such as mtDNA synthesis, cell growth, and cristae organization.[4]
In addition, HIGD1A helps preserve mitochondrial function by regulating mitochondrial γ-secretase activity under hypoxic conditions.[4][7] In the absence of HIGD1A, γ-secretase contributes to the accumulation of amyloid beta in the mitochondria, leading to increased ROS production, mitochondrial dysfunction, and eventually, cell death.[7]
While HIGD1A predominantly contributes to cell survival, it can also promote apoptosis in neurons during the early developmental stages of the central nervous system.[6]
Clinical significance
Since HIGD1A promotes cell survival under hypoxia, the protein protects organs like the heart and brain from hypoxia-related diseases.[5] In particular, HIGD1A localization to the nucleus correlates with the severity of stress in ischemic heart disease, hypoxic-ischemic encephalopathy, and cancer, and thus may serve as a biomarker for these diseases.[6] Moreover, HIGD1A is involved in inflammatory diseases, such as atherosclerosis and rheumatoid arthritis, through its role in macrophage survival.[5] Similarly, HIGD1A could become a key target for treating Alzheimer’s disease by inhibiting γ-secretase, and by extension, amyloid beta production. Notably, HIGD1A inhibits γ-secretase without interfering with Notch cleavage, thus minimizing detrimental side effects from targeting this protein.[7]
↑ 5.05.15.25.35.45.55.6An HJ, Shin H, Jo SG, Kim YJ, Lee JO, Paik SG, Lee H (Dec 2011). "The survival effect of mitochondrial Higd-1a is associated with suppression of cytochrome C release and prevention of caspase activation". Biochimica et Biophysica Acta. 1813 (12): 2088–98. doi:10.1016/j.bbamcr.2011.07.017. PMID21856340.
↑ 7.07.17.27.37.47.5Hayashi H, Nakagami H, Takeichi M, Shimamura M, Koibuchi N, Oiki E, Sato N, Koriyama H, Mori M, Gerardo Araujo R, Maeda A, Morishita R, Tamai K, Kaneda Y (Jun 2012). "HIG1, a novel regulator of mitochondrial γ-secretase, maintains normal mitochondrial function". FASEB Journal. 26 (6): 2306–17. doi:10.1096/fj.11-196063. PMID22355194.
Further reading
Maruyama K, Sugano S (Jan 1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID8125298.
Bonaldo MF, Lennon G, Soares MB (Sep 1996). "Normalization and subtraction: two approaches to facilitate gene discovery". Genome Research. 6 (9): 791–806. doi:10.1101/gr.6.9.791. PMID8889548.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, Suyama A, Sugano S (Oct 1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID9373149.
Denko N, Schindler C, Koong A, Laderoute K, Green C, Giaccia A (Feb 2000). "Epigenetic regulation of gene expression in cervical cancer cells by the tumor microenvironment". Clinical Cancer Research. 6 (2): 480–7. PMID10690527.
Mehrle A, Rosenfelder H, Schupp I, del Val C, Arlt D, Hahne F, Bechtel S, Simpson J, Hofmann O, Hide W, Glatting KH, Huber W, Pepperkok R, Poustka A, Wiemann S (Jan 2006). "The LIFEdb database in 2006". Nucleic Acids Research. 34 (Database issue): D415–8. doi:10.1093/nar/gkj139. PMC1347501. PMID16381901.
Ewing RM, Chu P, Elisma F, Li H, Taylor P, Climie S, McBroom-Cerajewski L, Robinson MD, O'Connor L, Li M, Taylor R, Dharsee M, Ho Y, Heilbut A, Moore L, Zhang S, Ornatsky O, Bukhman YV, Ethier M, Sheng Y, Vasilescu J, Abu-Farha M, Lambert JP, Duewel HS, Stewart II, Kuehl B, Hogue K, Colwill K, Gladwish K, Muskat B, Kinach R, Adams SL, Moran MF, Morin GB, Topaloglou T, Figeys D (2007). "Large-scale mapping of human protein-protein interactions by mass spectrometry". Molecular Systems Biology. 3 (1): 89. doi:10.1038/msb4100134. PMC1847948. PMID17353931.