CRISP1 is an epididymis-enriched, secreted CAP/CRISP-family glycoprotein that associates with the human sperm surface, including the postacrosomal sperm-head region. A tightly associated sperm pool promotes two successive fertilization steps: binding of sperm to the zona pellucida through a specific interaction with ZP3, and progression from sperm-oolemma binding to plasma-membrane fusion. Human CRISP1 also binds the calcium exporter PMCA4b through its N-terminal region and delays PMCA4b-mediated calcium extrusion in a heterologous assay, although the endogenous importance of this mechanism in human sperm remains unresolved. CRISP-family redundancy in mouse models indicates a modulatory, cooperative role rather than an indispensable standalone fusogen.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005576 extracellular region | IBA GO_REF:0000033 | ACCEPT | Summary: The PAINT extracellular-region inference agrees with CRISP1's signal peptide and with direct human localization in the epididymal lumen, seminal plasma, and on the sperm surface. Reason: Human tissue and immunohistochemical experiments identify CRISP1 as an epididymal secretory glycoprotein in luminal fluids and at the extracellular sperm surface. Its demonstrated zona-binding and gamete-fusion roles occur in this extracellular context, so the broad IBA term is correct. Supporting Evidence: PMID:8543280 This antibody detected a major band of 30 kD and a minor band of 26 kD in the caput, corpus, and cauda regions of the epididymis, the ductus deferens, the sperm, and the seminal plasma. |
| GO:0060090 molecular adaptor activity | IBA GO_REF:0000033 | REMOVE | Summary: PAINT propagated molecular adaptor activity to CRISP1 from a single mouse Glipr1l1 seed at a broad CAP-family ancestral node. Reason: The cached PTHR10334 trace places this activity at PTN000036124 using only MGI:MGI:1916536, mouse Glipr1l1. GLIPR1L1 is a distinct GPI-anchored sperm/acrosomal paralog implicated in organizing IZUMO1 redistribution. Human CRISP1 directly binds ZP3, participates in gamete fusion, and regulates PMCA4b, but no experiment shows it bringing multiple macromolecules together as required by molecular adaptor activity. The source annotation may be sound for Glipr1l1, but root-family propagation to CRISP1 is not. Propagation Review Root cause: PROPAGATION BAD Failure modes: WRONG ORTHOLOG OR PARALOG FUNCTIONAL DIVERGENCE ROLE CONFLATION Sources checked: MGI:MGI:1916536 · mouse Glipr1l1 SUPPORTS SOURCE BUT NOT TARGET The seed supports a sperm/acrosomal organizing role in a distinct GLIPR1-like paralog, not adaptor activity in CRISP1. PANTHER:PTN000036124 · broad PTHR10334 ancestral node UNRESOLVED This node spans functionally divergent CAP-family subfamilies and is too broad for transfer of the Glipr1l1-specific adaptor role. Supporting Evidence: file:human/CRISP1/CRISP1-deep-research-manual.md The cached PANTHER trace places GO:0060090 molecular adaptor activity at the broad PTHR10334 node PTN000036124 from only MGI:MGI:1916536, mouse `Glipr1l1`. |
| GO:0005576 extracellular region | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro maps the secreted CAP/CRISP architecture to extracellular region. Reason: The automated term is broad but independently supported by the N-terminal signal peptide and direct localization of human CRISP1 in epididymal lumen, seminal plasma, and on the extracellular sperm surface. Supporting Evidence: PMID:8543280 Immunohistochemical analysis showed that the human AEG-like molecule is located in the lumen and epithelium of distal ductus efferentes and epididymal ducts, and on the postacrosomal region of the sperm head. |
| GO:0005634 nucleus | HDA PMID:21630459 Proteomic characterization of the human sperm nucleus. | UNDECIDED | Summary: CRISP1 was assigned to the sperm nucleus from a large-scale proteomic catalogue, but the cached publication is abstract-only and does not list individual proteins. Reason: The abstract reports a highly purified sperm-nuclear preparation and 403 protein identifications, but it does not name CRISP1 or expose peptide-level evidence. Nuclear localization is unexpected for a secreted sperm-surface protein, yet the curator's full evidence cannot be checked from the cache. Following the incomplete-evidence rule, this experimental annotation is retained as unresolved rather than removed. Supporting Evidence: PMID:21630459 With this approach, 403 different proteins have been identified from the isolated sperm nuclei. |
| GO:0005576 extracellular region | TAS PMID:8543280 [Analysis of the human acidic epididymal glycoprotein-like m... | ACCEPT | Summary: The original human tissue study directly places CRISP1 in reproductive-duct lumina, seminal plasma, and on the sperm head. Reason: Although the TAS code is statement-level, the cited study reports antibody detection in sperm and seminal plasma and immunohistochemical localization in epididymal lumina. These observations directly support the broad extracellular-region annotation. Supporting Evidence: PMID:8543280 This antibody detected a major band of 30 kD and a minor band of 26 kD in the caput, corpus, and cauda regions of the epididymis, the ductus deferens, the sperm, and the seminal plasma. |
| GO:0007342 fusion of sperm to egg plasma membrane involved in single fertilization | TAS PMID:8838800 Characterization of a human glycoprotein with a potential ro... | ACCEPT | Summary: The original characterization proposed CRISP1 as the human functional counterpart of rodent AEG/DE; later direct human functional experiments support its participation after sperm-oolemma binding and before fusion. Reason: PMID:8838800 alone established secretion and postacrosomal sperm binding while proposing a fusion role. PMID:11566719 subsequently showed that anti-CRISP1 specifically inhibits penetration of zona-free eggs without impairing viability, motility, acrosome reaction, or initial oolemma binding, and demonstrated CRISP1-binding sites on human oocytes. The term is therefore supported, while CRISP1 should not be described as the sole indispensable fusogen. Supporting Evidence: PMID:8838800 Although this protein, designated ARP (AEG-related protein), is not the ortholog of rodent AEG, it resembles AEG in that it is an epididymal secretory glycoprotein that binds to the postacrosomal region of the sperm head. PMID:11566719 The antibody did not inhibit the occurrence of spontaneous or Ca(2+) ionophore-induced acrosome reaction, nor did it inhibit the ability of sperm to bind to the oolema, supporting a specific inhibition of the antibody at the sperm-egg fusion level. |
| GO:0007339 binding of sperm to zona pellucida | IDA PMID:24334245 Human fertilization: epididymal hCRISP1 mediates sperm-zona ... | NEW | Summary: Human CRISP1 promotes sperm binding to the zona pellucida through a direct, preferential interaction with ZP3. Reason: Anti-CRISP1 and recombinant CRISP1 independently reduced the number of human sperm bound in hemizona assays without affecting motility, capacitation-associated tyrosine phosphorylation, or acrosome reaction. Recombinant CRISP1 bound ZP3 dose-dependently and saturably, providing a specific direct mechanism for this missing process annotation. Supporting Evidence: PMID:24334245 Results revealed that both anti-hCRISP1 and rec-hCRISP1 produced a significant inhibition in the number of sperm bound per HZ compared with the corresponding controls. PMID:24334245 Results revealed that rec-hCRISP1 mainly interacted with ZP3 in a dose-dependent and saturable manner, supporting the specificity of this interaction. |
| GO:0097524 sperm plasma membrane | IDA PMID:11566719 Evidence that human epididymal protein ARP plays a role in g... | NEW | Summary: A tightly associated population of human CRISP1 is present at the sperm surface and is positioned to act during gamete interaction. Reason: Sequential extraction of ejaculated human sperm directly demonstrated a tightly sperm-surface-associated CRISP1 pool. Independent immunohistochemistry places CRISP1 on the postacrosomal sperm head, making sperm plasma membrane more informative than extracellular region alone. Supporting Evidence: PMID:11566719 Sequential extraction of proteins from ejaculated human sperm revealed the existence of a population of ARP that is tightly associated with the sperm surface and thus, potentially capable of participating in gamete interaction. |
| GO:1903170 negative regulation of calcium ion transmembrane transport | IDA PMID:37882330 Mammalian cysteine-rich secretory proteins interact with pla... | NEW | Summary: Human CRISP1 binds PMCA4b through its N-terminal domain and delays PMCA4b-mediated calcium extrusion in co-transfected cells. Reason: Direct co-immunoprecipitation and calcium assays distinguish human CRISP1 from CRISP3: both bind PMCA4b, but only CRISP1 delays transporter-mediated calcium extrusion. The process term captures the measured effect without overextending the rodent CatSper data to human calcium-channel regulator activity. Endogenous relevance in human sperm remains a knowledge gap. Supporting Evidence: PMID:37882330 Human CRISP1 (hCRISP1) and hCRISP3 also interacted with PMCA4b via the N-terminal domain. PMID:37882330 Interestingly, hCRISP1 and rCRISP4 delayed PMCA4b-mediated calcium extrusion but hCRISP3 did not. |
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Download this section (compressed HTML)Q: What is the human oolemma receptor for CRISP1, and does CRISP1 directly alter membrane fusion or organize a transient adhesion/signaling interface after initial sperm-oolemma binding?
Suggested experts: Patricia S. Cuasnicu, Debora J. Cohen
Q: Does endogenous human sperm CRISP1 regulate PMCA4b, CatSper, or both during capacitation and fertilization, and which CRISP1 domain mediates each effect?
Suggested experts: Bhagyashri R. Pathak, Patricia S. Cuasnicu
Q: Do the long and short CRISP1 isoforms differ in secretion, stable sperm-surface association, zona/fusion activity, or release during capacitation?
Suggested experts: Masaru Hayashi, Patricia S. Cuasnicu
Experiment: Use affinity-matured monovalent CRISP1 probes and proximity labeling on live zona-free human oocytes, followed by quantitative membrane proteomics and orthogonal receptor knockout or blocking assays in a validated gamete-fusion model.
Hypothesis: CRISP1 engages a specific oolemma receptor distinct from the initial sperm-binding machinery and promotes the transition to membrane fusion.
Type: receptor discovery, live-cell proximity labeling, and functional blocking
Experiment: Measure PMCA4b extrusion and CatSper currents in capacitated human sperm after acute CRISP1 depletion or isoform-specific blocking, then rescue with mammalian-expressed wild-type CRISP1 and CAP- or CRD-domain mutants.
Hypothesis: Endogenous human CRISP1 restrains calcium flux through separable PMCA4b- and channel-regulatory interfaces that tune rather than abolish fertilizing competence.
Type: human sperm electrophysiology, calcium imaging, and separation-of-function rescue
Experiment: Endogenously tag both CRISP1 isoforms in primary human epididymal organoids, trace secretion and sperm acquisition, and quantify loosely versus tightly associated pools before and after capacitation.
Hypothesis: Isoform identity and epididymal processing determine whether CRISP1 is released during capacitation or retained at the postacrosomal sperm membrane for gamete interaction.
Type: isoform-resolved genome editing, organoid secretomics, and sperm-surface biochemistry
Experiment: Reanalyze purified human sperm nuclei and matched membrane fractions with targeted CRISP1 peptides, isotope-labeled standards, and microscopy using knockout-validated antibodies.
Hypothesis: The historical sperm-nucleus HDA signal reflects residual membrane-associated CRISP1 rather than a reproducible intranuclear pool.
Type: targeted spatial proteomics and orthogonal localization
What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The direct human oolemma partner and molecular mechanism by which CRISP1 promotes sperm-egg plasma-membrane fusion are unknown.
OPEN BIOLOGY MF_DARK
What is known: Antibody inhibition places CRISP1 after initial oolemma binding, and recombinant CRISP1 binds the human oocyte surface, but neither experiment identifies the receptor or distinguishes adhesion, signaling, and membrane remodeling mechanisms.
Significance: Resolving the partner and activity is necessary to replace a process-only description with a precise molecular function and to assess contraceptive or infertility relevance.
What would resolve it: Live-oocyte receptor capture, direct binding kinetics, loss-of-function validation, and reconstituted membrane-fusion assays are required.
Provenance (the field's own admissions):
Gap: It is not known whether human CRISP1 regulates endogenous PMCA4b or calcium channels in human sperm during capacitation and fertilization.
OPEN BIOLOGY MF_DARK
What is known: Human CRISP1 directly binds and delays PMCA4b-mediated calcium extrusion in a heterologous system, while native rat CRISP1 regulates CatSper and TRPM8 in mouse sperm; the endogenous human connection has not been tested.
Significance: Calcium control could connect CRISP1's extracellular interactions to sperm motility, capacitation, and fusion and define its domain-specific molecular activities.
What would resolve it: Acute perturbation and electrophysiology in human sperm, endogenous interaction mapping, and separation-of-function rescue are needed.
Provenance (the field's own admissions):
Gap: The functional distinction between CRISP1 isoforms and loosely versus tightly sperm-associated pools is unresolved, and the reported sperm-nuclear pool is unverified.
OPEN BIOLOGYCURATION CC_DARK
What is known: Two UniProt isoforms exist; direct human studies detect both soluble reproductive-fluid and tightly sperm-surface-associated CRISP1, whereas the abstract-only nuclear proteomics source cannot be inspected at peptide level.
Significance: Pool and isoform resolution is required to assign where each activity occurs and to decide whether the nuclear HDA annotation is reproducible.
What would resolve it: Isoform-resolved endogenous tagging, pulse-chase/secretome analysis, surface extraction, targeted spatial proteomics, and validated microscopy should resolve the locations.
Provenance (the field's own admissions):
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