STAP1

STAP1 Full Name

signal transducing adaptor family member 1

STAP1 Introduction

STAP1 (signal-transducing adaptor family member 1) is a cytoplasmic adaptor protein characterized by a pleckstrin homology (PH) domain and a Src-homology 2 (SH2) domain, allowing it to localize to the plasma membrane in response to phosphoinositide lipids and to bind phosphotyrosine motifs on receptor complexes. STAP1 was originally identified as a docking protein for BCR–ABL and other tyrosine kinases and is now recognized as a key regulator of immune-cell signaling. The STAP1 gene maps to chromosome 4q13.3 and is predominantly expressed in lymphoid and myeloid cells.

Figure 1. The structure of STAP1.

Adaptor in B-Cell Receptor and Tyrosine Kinase Signaling
On B-cell receptor stimulation, STAP1 is recruited to the plasma membrane through its PH domain and binds phosphorylated ITAMs via its SH2 domain, creating a scaffold that brings Bruton's tyrosine kinase (BTK) and phospholipase Cγ2 into proximity. STAP1 also interacts with BCR–ABL and several receptor tyrosine kinases in hematopoietic cells, modulating their downstream MAPK and PI3K signaling output. Through these scaffolding functions, STAP1 amplifies proliferative and survival signals downstream of immune-receptor and oncogenic tyrosine kinases.

Autoimmune Disease and Leukemia
Genetic variants in STAP1 have been associated with susceptibility to several autoimmune diseases, including systemic lupus erythematosus and rheumatoid arthritis, where they may alter B-cell tolerance or activation thresholds. STAP1 overexpression has been reported in chronic lymphocytic leukemia and in BCR–ABL-positive acute lymphoblastic leukemia, where the adaptor contributes to leukemic cell survival. Disruption of the STAP1–BTK interaction by small molecules is being explored as a strategy to modulate B-cell signaling in autoimmune disease, complementary to direct BTK inhibitors.

Alternate Names for STAP1

STAP1; signal transducing adaptor family member 1; BRDG1; STAP-1; signal-transducing adaptor protein 1; docking protein BRDG1; BCR downstream signaling 1; stem cell adaptor protein 1; BCR downstream-signaling protein 1; signal-transducing adaptor protein-1;