Seroatlas · Human Serome Atlas

SIT1

Signaling threshold-regulating transmembrane adapter 1

Also known as: SIT, SIT1_HUMAN

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

Protein identityUniProt · HPA

UniProt accession: Q9Y3P8
Gene: SIT1
Ensembl: ENSG00000137078
Chromosome: 9
Canonical length: 196 aa
Protein class: Predicted membrane proteins
Quaternary structure: Homodimer

OverviewNCBI Gene

Enables kinase binding activity. Involved in regulation of T cell activation. Located in plasma membrane. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

196 residues, UniProt reviewed canonical sequence.

>Q9Y3P8|SIT1
     1  MNQADPRLRA VCLWTLTSAA MSRGDNCTDL LALGIPSITQ AWGLWVLLGA VTLLFLISLA
    61  AHLSQWTRGR SRSHPGQGRS GESVEEVPLY GNLHYLQTGR LSQDPEPDQQ DPTLGGPARA
   121  AEEVMCYTSL QLRPPQGRIP GPGTPVKYSE VVLDSEPKSQ ASGPEPELYA SVCAQTRRAR
   181  ASFPDQAYAN SQPAAS

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against SIT1 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: Cell surface
Secreted: No
Transmembrane segments: 1
Mean surface accessibility (rSASA): 0.67
Highest tissue expression: 88 nTPM

Expression across tissuesHPA

Tissue

thymus: 88 nTPM
lymph node: 47 nTPM
tonsil: 31 nTPM
spleen: 22 nTPM
appendix: 18 nTPM
small intestine: 12 nTPM

Single-cell type

pdcs: 78 nCPM
t-cells: 67 nCPM
b-cells: 43 nCPM
plasma cells: 18 nCPM
extravillous trophoblasts: 3.1 nCPM
kupffer cells: 3.1 nCPM

Immune cell

T-reg: 354 nTPM
memory CD4 T-cell: 251 nTPM
memory CD8 T-cell: 224 nTPM
memory B-cell: 215 nTPM
MAIT T-cell: 204 nTPM
plasmacytoid DC: 202 nTPM

Brain region

thalamus: 1.3 nTPM
pons: 0.7 nTPM
medulla oblongata: 0.5 nTPM
white matter: 0.4 nTPM
hypothalamus: 0.3 nTPM
spinal cord: 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): 1.19
gnomAD pLI: 0
gnomAD missense Z: 1.17
DepMap mean gene effect: -0.05
DepMap dependency class: selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 3% 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

Signaling threshold-regulating transmembrane adapter 1

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of SIT1 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 SIT1 as an antibody target. Whether an autoantibody or antibody against SIT1 could matter depends on whether native SIT1 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

SIT1 is annotated at the cell surface, where native SIT1 is exposed to circulating antibodies and is a prime autoantibody target that could block, deplete, or overstimulate it.

Annotation status

The present source text does not explicitly label SIT1 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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