ACP1

ACP1 Full Name

acid phosphatase 1, soluble

ACP1 Introduction

Acid phosphatase 1, soluble (ACP1), widely recognized in molecular biology as low molecular weight protein tyrosine phosphatase (LMW-PTP), is a highly conserved 18 kDa cytosolic enzyme. Despite its historical classification as an acid phosphatase, ACP1 functions fundamentally as a protein tyrosine phosphatase (PTP). The ACP1 gene, located on chromosome 2, undergoes alternative splicing to produce two primary functional isoforms—fast and slow (or A and B)—both of which are ubiquitously expressed across human tissues. The core biological function of ACP1 is to modulate intracellular signaling pathways by dephosphorylating specific tyrosine residues on various target proteins. Its primary substrates include critical receptor tyrosine kinases (RTKs) such as the insulin receptor, platelet-derived growth factor receptor (PDGFR), and EphA2, as well as downstream signaling effectors like β-catenin and Src. By dynamically acting as an "off-switch" for the phosphorylation state of these molecules, ACP1 serves as a pivotal regulator controlling cell proliferation, cellular adhesion, cytoskeletal remodeling, and energy metabolism.

Figure 1. Model explaining the proposed role of LMW-PTP in the FAK-mediated inhibition of LFA-1 and TCR reorganization into clusters. (Source: Giannoni E, et al. 2003)

Clinically, the dysregulation of ACP1 is strongly implicated in metabolic disorders and various malignancies, making it a critical biomarker and therapeutic target. Because ACP1 naturally dephosphorylates and inactivates the insulin receptor, its pathological upregulation is frequently associated with diminished insulin signaling. Consequently, elevated ACP1 activity is considered a significant contributing factor to the pathogenesis of insulin resistance, type 2 diabetes, and obesity-related metabolic syndromes. In the field of oncology, ACP1 plays a complex, context-dependent role. While initially thought to act solely as a tumor suppressor by counteracting growth factor receptors, extensive recent clinical evidence reveals that ACP1 is frequently overexpressed in aggressive human cancers, including breast, colorectal, and prostate carcinomas. In these malignant microenvironments, ACP1 often functions as an oncogene. By dephosphorylating specific substrates (such as p190RhoGAP), it triggers the activation of RhoA, heavily promoting tumor cell motility, invasion, and metastasis. Furthermore, an altered ratio between its fast and slow isoforms is increasingly recognized as an indicator of tumor aggressiveness and poor patient prognosis.

Alternate Names for ACP1

ACP1; acid phosphatase 1, soluble; HAAP; low molecular weight phosphotyrosine protein phosphatase; LMW-PTP; LMW-PTPase; adipocyte acid phosphatase; red cell acid phosphatase 1; protein tyrosine phosphatase; acid phosphatase of erythrocyte

• 1. Giannoni E, et al. Lymphocyte function-associated antigen-1-mediated T cell adhesion is impaired by low molecular weight phosphotyrosine phosphatase-dependent inhibition of FAK activity. J Biol Chem. 2003 Sep 19;278(38):36763-76.
  2. Alho I, et al. The role of low-molecular-weight protein tyrosine phosphatase (LMW-PTP ACP1) in oncogenesis. Tumour Biol. 2013 Aug;34(4):1979-89.