GJB1 Membrane Protein Introduction

Introduction of GJB1

The gap junction beta-1 protein (GJB1) is a transmembrane protein that is encoded by the GJB1 gene in humans. It is also known as connexin 32 (Cx32). The GJB1 gene is approximately 10 kb in length, consisting of an encoding exon and three non-coding exons. GJB1 is a member of the gap junction connexin protein family, which is responsible for regulating and controlling the transmission of signals on the cell membrane, primarily in the liver and peripheral nervous system. This protein contains four transmembrane domains, combined to form gap junctions.

Basic Information of GJB1
Protein Name	Gap junction beta-1 protein
Gene Name	GJB1
Aliases	Connexin-32
Organism	Homo sapiens (Human)
UniProt ID	P08034
Transmembrane Times	4
Length (aa)	283
Sequence	MNWTGLYTLLSGVNRHSTAIGRVWLSVIFIFRIMVLVVAAESVWGDEKSSFICNTLQPGCNSVCYDQFFPISHVRLWSLQLILVSTPALLVAMHVAHQQHIEKKMLRLEGHGDPLHLEEVKRHKVHISGTLWWTYVISVVFRLLFEAVFMYVFYLLYPGYAMVRLVKCDVYPCPNTVDCFVSRPTEKTVFTVFMLAASGICIILNVAEVVYLIIRACARRAQRRSNPPSRKGSGFGHRLSPEYKQNEINKLLSEQDGSLKDILRRSPGTGAGLAEKSDRCSAC

Function of GJB1 Membrane Protein

Connexins contain a family of >20 homologous integral membrane proteins that form gap junction channels, providing a pathway for the diffusion of small molecules and ions between adjacent cells. GJB1 is a gap junction and the beta-1 protein is also identified as connexin 32 with 238 amino acids. Connexin-32 is mainly expressed in oligodendrocytes. The GJB1 protein is present in many organs, including the liver, kidney, pancreas and nervous system. In normal conditions, this protein is located in the cell membrane of Schwann cells and oligodendrocytes, which are specialized cells of the nervous system. In general, GJB1 proteins form channels through myelin to internal Schwann cells or oligodendrocytes for efficient transportation and communication. Mutations of the GJB1 gene affect gap junction signaling and trafficking, leading to a hereditary peripheral neuropathy, known as X-linked sacral muscular atrophy. GJB1 acts as a radial diffusion pathway, allowing the transfer and diffusion of nutrients, ions and small molecules between cells.

Fig.1 The structure of GJB1. (Kleopa, 2012)

Application of GJB1 CX32 Membrane Protein in Literature

Abrams C.K., et al. Functional Requirement for a Highly Conserved Charged Residue at Position 75 in the Gap Junction Protein Connexin 32. The Journal of Biological Chemistry. 2013, (5): 3609–3619. PubMed ID: 23209285

The study showed that CMT1X's disease treatment strategy corrected trafficking abnormalities in GJB1, which may be ineffective for the mutant group, and it also altered the properties of the GJB1-channel gate.
Liu X.M., et al. PBX1 Attributes as a Determinant of Connexin 32 Downregulation in Helicobacter Pylori-Related Gastric Carcinogenesis. World Journal of Gastroenterology. 2017, (29): 5345–5355. PubMed ID: 28839434

This article reveals that PBX1 is one of the determinants of the GJB1 promoter target site, preventing further damage associated with gastric cancer.
Sadowska G.B., et al. Ontogeny of Connexin 32 and 43 Expression in the Cerebral Cortices of Ovine Fetuses, Newborns, and Adults. Brain research.2009, 1255: 51–56. PubMed ID: 19101525

Studies have shown that GJB1 shows a corresponding reduction in the late fetal development of newborn and adult sheep.
Batir Y., et al. Structural Studies of N-Terminal Mutants of Connexin 26 and Connexin 32 Using 1H NMR Spectroscopy. Archives of biochemistry and biophysics. 2016, 608: 8–19. PubMed ID: 27378082

The authors note that in the homomeric channel, the inflexible GJB1G12R n-terminal block ion conduction and this channel block can be alleviated by the addition of wild-type subunits.
Qin J., et al. Connexin 32-Mediated Cell-Cell Communication Is Essential for Hepatic Differentiation from Human Embryonic Stem Cells. Scientific Reports. 2016, 6: 37388. PubMed ID: 27874032

These results indicate that GJB1 is critical for cell-cell interactions, thereby promoting hepatocyte maturation and maturation.

GJB1 Preparation Options

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Reference

Kleopa K A., et al. (2012). How do Mutations in GJB1 Cause X-linked Charcot-Marie-Tooth Disease? Brain Research. 1487.17, 198-205.

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