| Structural highlights
Disease
[HEXB_HUMAN] Defects in HEXB are the cause of GM2-gangliosidosis type 2 (GM2G2) [MIM:268800]; also known as Sandhoff disease. GM2-gangliosidosis is an autosomal recessive lysosomal storage disease marked by the accumulation of GM2 gangliosides in the neuronal cells. GM2G2 is clinically indistinguishable from GM2-gangliosidosis type 1, presenting startle reactions, early blindness, progressive motor and mental deterioration, macrocephaly and cherry-red spots on the macula.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
Function
[HEXB_HUMAN] Responsible for the degradation of GM2 gangliosides, and a variety of other molecules containing terminal N-acetyl hexosamines, in the brain and other tissues.
Publication Abstract from PubMed
GM2 gangliosidoses, including Tay-Sachs and Sandhoff diseases, are neurodegenerative lysosomal storage diseases that are caused by deficiency of beta-hexosaminidase A, which comprises an alphabeta heterodimer. There are no effective treatments for these diseases; however, various strategies aimed at restoring beta-hexosaminidase A have been explored. Here, we produced a modified human hexosaminidase subunit beta (HexB), which we have termed mod2B, composed of homodimeric beta subunits that contain amino acid sequences from the alpha subunit that confer GM2 ganglioside-degrading activity and protease resistance. We also developed fluorescent probes that allow visualization of endocytosis of mod2B via mannose 6-phosphate receptors and delivery of mod2B to lysosomes in GM2 gangliosidosis models. In addition, we applied imaging mass spectrometry to monitor efficacy of this approach in Sandhoff disease model mice. Following i.c.v. administration, mod2B was widely distributed and reduced accumulation of GM2, asialo-GM2, and bis(monoacylglycero)phosphate in brain regions including the hypothalamus, hippocampus, and cerebellum. Moreover, mod2B administration markedly improved motor dysfunction and a prolonged lifespan in Sandhoff disease mice. Together, the results of our study indicate that mod2B has potential for intracerebrospinal fluid enzyme replacement therapy and should be further explored as a gene therapy for GM2 gangliosidoses.
Protease-resistant modified human beta-hexosaminidase B ameliorates symptoms in GM2 gangliosidosis model.,Kitakaze K, Mizutani Y, Sugiyama E, Tasaki C, Tsuji D, Maita N, Hirokawa T, Asanuma D, Kamiya M, Sato K, Setou M, Urano Y, Togawa T, Otaka A, Sakuraba H, Itoh K J Clin Invest. 2016 May 2;126(5):1691-703. doi: 10.1172/JCI85300. Epub 2016 Mar, 28. PMID:27018595[11]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Banerjee P, Siciliano L, Oliveri D, McCabe NR, Boyers MJ, Horwitz AL, Li SC, Dawson G. Molecular basis of an adult form of beta-hexosaminidase B deficiency with motor neuron disease. Biochem Biophys Res Commun. 1991 Nov 27;181(1):108-15. PMID:1720305
- ↑ Wakamatsu N, Kobayashi H, Miyatake T, Tsuji S. A novel exon mutation in the human beta-hexosaminidase beta subunit gene affects 3' splice site selection. J Biol Chem. 1992 Feb 5;267(4):2406-13. PMID:1531140
- ↑ Bolhuis PA, Ponne NJ, Bikker H, Baas F, Vianney de Jong JM. Molecular basis of an adult form of Sandhoff disease: substitution of glutamine for arginine at position 505 of the beta-chain of beta-hexosaminidase results in a labile enzyme. Biochim Biophys Acta. 1993 Sep 8;1182(2):142-6. PMID:8357844
- ↑ Kuroki Y, Itoh K, Nadaoka Y, Tanaka T, Sakuraba H. A novel missense mutation (C522Y) is present in the beta-hexosaminidase beta-subunit gene of a Japanese patient with infantile Sandhoff disease. Biochem Biophys Res Commun. 1995 Jul 17;212(2):564-71. PMID:7626071 doi:https://dx.doi.org/10.1006/bbrc.1995.2007
- ↑ Gomez-Lira M, Sangalli A, Mottes M, Perusi C, Pignatti PF, Rizzuto N, Salviati A. A common beta hexosaminidase gene mutation in adult Sandhoff disease patients. Hum Genet. 1995 Oct;96(4):417-22. PMID:7557963
- ↑ Zhang ZX, Wakamatsu N, Akerman BR, Mules EH, Thomas GH, Gravel RA. A second, large deletion in the HEXB gene in a patient with infantile Sandhoff disease. Hum Mol Genet. 1995 Apr;4(4):777-80. PMID:7633435
- ↑ Redonnet-Vernhet I, Mahuran DJ, Salvayre R, Dubas F, Levade T. Significance of two point mutations present in each HEXB allele of patients with adult GM2 gangliosidosis (Sandhoff disease) homozygosity for the Ile207-->Val substitution is not associated with a clinical or biochemical phenotype. Biochim Biophys Acta. 1996 Nov 15;1317(2):127-33. PMID:8950198
- ↑ Narkis G, Adam A, Jaber L, Pennybacker M, Proia RL, Navon R. Molecular basis of heat labile hexosaminidase B among Jews and Arabs. Hum Mutat. 1997;10(6):424-9. PMID:9401004 doi:<424::AID-HUMU2>3.0.CO;2-D 10.1002/(SICI)1098-1004(1997)10:6<424::AID-HUMU2>3.0.CO;2-D
- ↑ Fujimaru M, Tanaka A, Choeh K, Wakamatsu N, Sakuraba H, Isshiki G. Two mutations remote from an exon/intron junction in the beta-hexosaminidase beta-subunit gene affect 3'-splice site selection and cause Sandhoff disease. Hum Genet. 1998 Oct;103(4):462-9. PMID:9856491
- ↑ Hou Y, McInnes B, Hinek A, Karpati G, Mahuran D. A Pro504 --> Ser substitution in the beta-subunit of beta-hexosaminidase A inhibits alpha-subunit hydrolysis of GM2 ganglioside, resulting in chronic Sandhoff disease. J Biol Chem. 1998 Aug 14;273(33):21386-92. PMID:9694901
- ↑ Kitakaze K, Mizutani Y, Sugiyama E, Tasaki C, Tsuji D, Maita N, Hirokawa T, Asanuma D, Kamiya M, Sato K, Setou M, Urano Y, Togawa T, Otaka A, Sakuraba H, Itoh K. Protease-resistant modified human beta-hexosaminidase B ameliorates symptoms in GM2 gangliosidosis model. J Clin Invest. 2016 May 2;126(5):1691-703. doi: 10.1172/JCI85300. Epub 2016 Mar, 28. PMID:27018595 doi:https://dx.doi.org/10.1172/JCI85300
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