Biology subjects

Wennemuth, G.

Publications and source records attributed to Wennemuth, G..

4 recordsLinked to original sources

bioRxiv2026

Soluble ZP2 N-terminal fragments activate CatSper-dependent Ca2+ entry and regulate motility and acrosomal exocytosis in mammalian sperm

Sperm motility and function are central to mammalian fertilization and are tightly regulated by intracellular calcium (CaCa2+) signaling. This signaling is primarily orchestrated by the CatSper Ca2+; channel complex located in the flagella of spermatozoa. However, the natural ligands that activate CatSper remain largely unknown in many species, despite the conservation of CatSper in mammals. Here, we present a signaling role for soluble N-terminal ZP2 fragments in regulating CatSper activity and sperm physiology in mice and humans. ZP2 has been implicated in mediating sperm binding and recognition at the oocyte surface interface; however, new evidence is starting to unveil the molecular mechanisms and function of ZP2 during fertilization transition. Here, we show that the during fertilization, cleaved ZP2 N-terminal fragment triggers a rapid and robust increase in intracellular CaCa2+ levels in sperm. This increase depends strictly on CatSper function, as demonstrated through pharmacological analysis and CatSper1 knockout mice. This calcium influx is sufficient to induce acrosomal exocytosis in a subset of human and mouse sperm. AlphaFold-based structural modeling suggests a potentially conserved extracellular interaction site between the soluble N-terminal ZP2 fragments and the CatSper complex. In human sperm, ZP2 treatment significantly modulates motility parameters, including flagellar movement and velocity, while inducing a CatSper-dependent increase in intracellular CaCa2+ similar in magnitude to that evoked by progesterone. Species-matched ZP2 stimulation elicits the stronger calcium response, underscoring evolutionary adaptations in ligand-channel protein pairs. Taken together, our findings reveal a conserved signaling pathway from ZP2 to CatSper that integrates oocyte-derived signals into the regulation of sperm motility and acrosomal exocytosis. This pathway provides new mechanistic insights into fertilization and highlights potential targets.

cell biology↗

bioRxiv2025

Coordinated and compartmentalized functions of CAII and CAIV establish a dual pH-regulatory mechanism essential for sperm maturation and capacitation

Carbonic anhydrase II (CAII) and IV (CAIV) orchestrate pH regulation essential for male fertility through distinct cellular compartments, with CAII functioning intracellularly and CAIV GPI-anchored extracellularly in epididymal and vas deferens epithelia as well as on spermatozoa. These enzymes control pH environments required for sperm maturation and capacitation by regulating bicarbonate availability, which triggers soluble adenylyl cyclase/cAMP signaling, elevates intracellular pH (pHi), and enables motility activation. However, the specific contributions of CAII and CAIV to luminal pH and sperm pHi regulation remain unclear. Here, we show that genetic ablation of either CAII or CAIV in mice impairs normal luminal acidification in the male reproductive tract and unexpectedly lowers the basal pHi of sperm. This lower basal pHi blunts subsequent intracellular alkalinization, thereby diminishing the activation of pH-sensitive CatSper Ca2+ channels essential for hyperactivated motility. Mechanistically, we demonstrate that this basal pHi reduction occurs independently of the CatSper channel itself, but it is phenocopied in K+channel Slo3-deficient sperm, suggesting a homeostatic link between flagellar pH and membrane potential. Super-resolution imaging reveals that CAII is located within the flagellum near the CatSper channel in the principal piece, while CAIV is distributed along the entire flagellar membrane. Together, our findings demonstrate that CAII and CAIV employ spatially coordinated mechanisms to regulate pH. By maintaining an acidic luminal environment for sperm maturation and priming the subsequent alkalinization of sperm pHi, these enzymes modulate downstream ion channel activity to govern sperm motility and fertility. One-sentence summarySpatially coordinated carbonic anhydrases II and IV govern sperm motility by establishing the dual-compartment pH environments necessary to activate downstream flagellar ion channels.

cell biology↗

bioRxiv2025

LILRA5 functions to induce ROS production on innate immune cells

Activating immune receptors provide mechanisms for phagocytes to elicit important effector functions that promote the killing of microbes. Leukocyte immunoglobulin-like receptor A5 (LILRA5) an orphan immune receptor expressed by human phagocytes and co-localising with FcR{gamma}, remains poorly characterised. To address this, we developed a highly-specific anti-LILRA5 monoclonal antibody that has agonistic properties. Using a specific anti-LILRA5 antibody, we show LILRA5 expression on naive monocytes and neutrophils, and that ligation of LILRA5 stimulates ROS production. While increased LILRA5 transcript copy numbers have been associated with sepsis, we also observed increased levels in patients with systemic infection but without sepsis complications. Ex vivo bacterial infection of whole blood did not alter surface LILRA5 expression, but LPS stimulation changed expression levels. This indicates that surface LILRA5 expression is dynamic and likely regulated posttranscriptionally, changing responses to different stimuli or over time. Soluble (s)LILRA5 was enhanced in sera from sepsis patients and in supernatants of monocytes that were LPS-stimulated, indicative that shedding of LILRA5 from cell surfaces or that expression of sLILRA5 isoforms provides a mechanism to regulate surface LILRA5 expression levels. Finally, we show that altered surface LILRA5 expression influences LILRA5-induced ROS production capacity. We propose that LILRA5 is a dynamically regulated activating receptor expressed on phagocytes that can stimulate ROS production.

immunology↗

bioRxiv2021

3D structure and in situ arrangements of CatSper channel in the sperm flagellum

The sperm calcium channel CatSper plays a central role in successful fertilization as a primary Ca2+ gateway into the sperm flagellum. However, CatSpers complex subunit composition has impeded its reconstitution in vitro and structural elucidation. Here, we applied cryo-electron tomography to visualize the macromolecular organization of the native CatSper channel complex in intact mammalian sperm, as well as identified three additional CatSper-associated proteins. The repeating CatSper units form long zigzag-rows in four nanodomains along the flagella. In both mouse and human sperm, each CatSper repeat consists of a tetrameric pore complex. Murine CatSper contains an additional outwardly directed wing-structure connected to the tetrameric channel. The majority of the extracellular domains form a canopy above each pore-forming channel that interconnects to a zigzag-shaped roof. The intracellular domains link two neighboring channel complexes to a diagonal array. The loss of this intracellular link in Efcab9-/- sperm distorts the longitudinally aligned zigzag pattern and compromises flagellar movement. This work offers unique insights into the mechanisms underlying the assembly and transport of the CatSper complex to generate the nanodomains and provides a long-sought structural basis for understanding CatSper function in the regulation of sperm motility.

biophysics↗