Seroatlas · Human Serome Atlas

SPAG4

Sperm-associated antigen 4 protein

Also known as: CT127, SPAG4_HUMAN, SUN4

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession: Q9NPE6
Gene: SPAG4
Ensembl: ENSG00000061656
Chromosome: 20
Canonical length: 437 aa
Protein class: Predicted intracellular proteins, Predicted membrane proteins
Quaternary structure: Homodimer

OverviewNCBI Gene

The mammalian sperm flagellum contains two cytoskeletal structures associated with the axoneme: the outer dense fibers surrounding the axoneme in the midpiece and principal piece and the fibrous sheath surrounding the outer dense fibers in the principal piece of the tail. Defects in these structures are associated with abnormal tail morphology, reduced sperm motility, and infertility. In the rat, the protein encoded by this gene associates with an outer dense fiber protein via a leucine zipper motif and localizes to the microtubules of the manchette and axoneme during sperm tail development. Alternative splicing results in multiple transcript variants encoding different isoforms. [provided by RefSeq, Dec 2015]

Canonical amino-acid sequenceUniProt

437 residues, UniProt reviewed canonical sequence.

>Q9NPE6|SPAG4
     1  MRRSSRPGSA SSSRKHTPNF FSENSSMSIT SEDSKGLRSA EPGPGEPEGR RARGPSCGEP
    61  ALSAGVPGGT TWAGSSQQKP APRSHNWQTA CGAATVRGGA SEPTGSPVVS EEPLDLLPTL
   121  DLRQEMPPPR VFKSFLSLLF QGLSVLLSLA GDVLVSMYRE VCSIRFLFTA VSLLSLFLSA
   181  FWLGLLYLVS PLENEPKEML TLSEYHERVR SQGQQLQQLQ AELDKLHKEV STVRAANSER
   241  VAKLVFQRLN EDFVRKPDYA LSSVGASIDL QKTSHDYADR NTAYFWNRFS FWNYARPPTV
   301  ILEPHVFPGN CWAFEGDQGQ VVIQLPGRVQ LSDITLQHPP PSVEHTGGAN SAPRDFAVFG
   361  LQVYDETEVS LGKFTFDVEK SEIQTFHLQN DPPAAFPKVK IQILSNWGHP RFTCLYRVRA
   421  HGVRTSEGAE GSAQGPH

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against SPAG4 can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability: Intracellular
Secreted: No
Transmembrane segments: 2
Mean surface accessibility (rSASA): 0.49
Highest tissue expression: 85 nTPM

Expression across tissuesHPA

Tissue

pancreas: 85 nTPM
testis: 30 nTPM
spleen: 12 nTPM
pituitary gland: 8.2 nTPM
ovary: 7.9 nTPM
salivary gland: 7.1 nTPM

Single-cell type

plasma cells: 344 nCPM
early spermatids: 216 nCPM
late spermatids: 190 nCPM
late primary spermatocytes: 67 nCPM
pancreatic acinar cells: 56 nCPM
epicardial cells: 55 nCPM

Immune cell

plasmacytoid DC: 1.2 nTPM
T-reg: 0.4 nTPM
intermediate monocyte: 0.2 nTPM
memory B-cell: 0.2 nTPM
MAIT T-cell: 0.1 nTPM
memory CD8 T-cell: 0.1 nTPM

Brain region

cerebral cortex: 8.3 nTPM
midbrain: 7 nTPM
pons: 7 nTPM
medulla oblongata: 5.4 nTPM
basal ganglia: 5.2 nTPM
choroid plexus: 5.1 nTPM

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance): 0.95
gnomAD pLI: 0
gnomAD missense Z: 0.98
DepMap mean gene effect: -0.21
DepMap dependency class: selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 6% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Molecular functions

Cellular components

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of SPAG4 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads SPAG4 as an antibody target. Whether an autoantibody or antibody against SPAG4 could matter depends on whether native SPAG4 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

SPAG4 is annotated as predominantly intracellular. Intracellular proteins are common autoantibody markers, becoming visible to the immune system after cell injury or altered processing, but are usually markers of disease rather than direct drivers.

Annotation status

The present source text does not explicitly label SPAG4 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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