Seroatlas · Human Serome Atlas

SPMIP8

Sperm microtubule inner protein 8

Also known as: SMIP8_HUMAN, TEPP

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

Protein identityUniProt · HPA

UniProt accession: Q6URK8
Gene: SPMIP8
Ensembl: ENSG00000159648
Chromosome: 16
Canonical length: 216 aa
Protein class: Predicted intracellular proteins

OverviewNCBI Gene

Predicted to be involved in flagellated sperm motility. Predicted to be located in cytoplasm; cytoskeleton; and motile cilium. Predicted to be active in axonemal A tubule inner sheath and sperm flagellum. [provided by Alliance of Genome Resources, Apr 2025]

Canonical amino-acid sequenceUniProt

216 residues, UniProt reviewed canonical sequence.

>Q6URK8|SPMIP8
     1  MARIIDLVPW DDGSTHVYAS PAILLPMERQ RNQLAGVKQQ LYHPALPTLR HMDRDTVKAC
    61  LPDEHCQSTT YCRKDEFDNA HFTLLGVPNK PLQCLDITAT GQKLRNRYHE GKLAPIAPGI
   121  NRVDWPCFTR AIEDWSHFVS SAGEFKLPCL RKRAEGLSGY AVRYLKPDVT QTWRYCLSQN
   181  PSLDRYGQKP LPFDSLNTFR SFGSSYSRVN YLTPWH

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against SPMIP8 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: 0
Mean surface accessibility (rSASA): 0.55
Highest tissue expression: 9.6 nTPM

Expression across tissuesHPA

Tissue

testis: 9.6 nTPM
thyroid gland: 2 nTPM
urinary bladder: 0.6 nTPM
cervix: 0.5 nTPM
ovary: 0.5 nTPM
vagina: 0.5 nTPM

Single-cell type

late spermatids: 595 nCPM
early spermatids: 470 nCPM
late primary spermatocytes: 77 nCPM
urothelial cells: 17 nCPM
esophageal apical cells: 15 nCPM
megakaryocytes: 12 nCPM

Immune cell

naive CD8 T-cell: 1.3 nTPM
memory CD4 T-cell: 0.9 nTPM
naive CD4 T-cell: 0.8 nTPM
MAIT T-cell: 0.7 nTPM
memory CD8 T-cell: 0.6 nTPM
T-reg: 0.6 nTPM

Brain region

hypothalamus: 0.6 nTPM
basal ganglia: 0.4 nTPM
amygdala: 0.3 nTPM
cerebral cortex: 0.3 nTPM
medulla oblongata: 0.3 nTPM
midbrain: 0.3 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): 0.99
gnomAD pLI: 0
DepMap mean gene effect: 0.06
DepMap dependency class: none

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 4% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

flagellated sperm motility

Cellular components

Protein domainsUniProt · Pfam · InterPro

Sperm microtubule inner protein 8
Sperm microtubule inner protein 8

KeywordsUniProt

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads SPMIP8 as an antibody target. Whether an autoantibody or antibody against SPMIP8 could matter depends on whether native SPMIP8 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

SPMIP8 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 SPMIP8 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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