Crystal structure of TEX101, a glycoprotein essential for male fertility, reveals the presence of tandemly arranged Ly6/uPAR domains

Abstract

Testis‐expressed gene 101 (TEX101) is a glycosyl‐phosphatidylinositol‐anchored glycoprotein essential for sperm fertility and spermatogenesis. TEX101 interacts with lymphocyte antigen 6 complex, locus K (Ly6k) as well as a disintegrin and metallopeptidase domain 3 (ADAM3). Although these proteins are considered essential for fertility, the associated mechanisms remain uncharacterized. Herein, we determined the crystal structure of human and mouse TEX101, revealing that TEX101 contains two tandem Ly6/uPAR (LU) domains. Detailed structural analyses revealed characteristic surfaces of TEX101 that may be involved in the interactions with other proteins or membranes. These results provide the structural basis for the role of TEX101 in fertilization and could contribute to developing diagnostic methods and treatments for infertility or developing male contraceptives.

A Role of the TEX101 Interactome in the Common Aetiology Behind Male Subfertility and Testicular Germ Cell Tumor

“…The crystal structure of the TEX101 proteins in Homo sapiens and Mus musculus , which has 55% sequence similarity (Uniprot - Supplementary 2 ), has been compared. Both the overall structure and the electrostatic surface potential showed high similarity between the two, indicating that TEX101 might have similar functions in humans and mice ( 32 ).…”

“…Another related gene, not just for male fertility but also for the function of TEX101 , is the Ly6k gene. Although the co-expression of putative homologs in Mus musculus and Rattus norvegicus has a low co-expression score of 0.06, its high co-mention score in PubMed articles gives it a score of 0.9 ( 3 , 32 , 42 ). Ly6k is shown to be involved particularly in the migration of the sperm to the oviduct and the binding of the sperm to the ovum’s zona pellucida in mice models ( 42 , 54 ).…”

Targeting the Urokinase-Type Plasminogen Activator Receptor (uPAR) in Human Diseases With a View to Non-invasive Imaging and Therapeutic Intervention

“…This is indeed remarkable, as that disulfide bond connecting cysteine 7 and 8 is essential for the correct folding and stability of single LU domain proteins such as SLURP-1 ( Adeyo et al, 2015 ), GPIHBP1 ( Beigneux et al, 2015 ; Kristensen et al, 2021 ), CD59 ( Petranka et al, 1996 ), and κ-bungarotoxin ( Grant et al, 1998 ). Akin to uPAR, other multidomain members of the LU gene superfamily (e.g., Haldisin, C4.4A, TEX101) also lack this particular disulfide bond, but notably only in their N-terminal LU domain ( Kjaergaard et al, 2008 ; Gårdsvoll et al, 2013 ; Jiang et al, 2020 ; Masutani et al, 2020 ). The evolutionary deletion of the 7–8 disulfide bond in uPAR DI has functional consequences as its reintroduction into recombinant human uPAR impairs both uPA-binding and the dynamic association between uPAR domain DI and uPAR domains DIIDIII in the unoccupied receptor ( Mertens et al, 2012 ; Leth et al, 2019b ).…”

“…Residues facing the hydrophobic ligand-binding cavity are shown in green. (B) The atomic structures of multi-LU-domain members of the Ly6/uPAR gene superfamily: uPAR with three consecutive LU domains ( Xu et al, 2012 ; Zhao et al, 2015 ) and C4.4A ( Jiang et al, 2020 ) and TEX101 ( Masutani et al, 2020 ) each with two LU domains. The X-ray structures are shown in a cartoon representation with the β-sheets colored cyan (DI; N-terminal domain), magenta (DII), and blue (DIII) while the disulfide bonds are shown as yellow sticks.…”

Role of the Glycosylphosphatidylinositol-Anchored Protein TEX101 and Its Related Molecules in Spermatogenesis

“…In fact, various ions are mediated with important functions of sperm, such as the acrosomal reaction and hyperactivation of the motility, so that ion channels are deeply involved in control. With respect to TEX101, recent crystal structure analysis provides direct evidence that this molecule actually has two LU domains, both of which have a TFPD [ 85 ]. It is striking that such structural analysis holds great promise for elucidating the actual interactions between this molecule and a group of molecules associated with the ion channels.…”