IMR Press / FBL / Volume 8 / Issue 4 / DOI: 10.2741/941

Frontiers in Bioscience-Landmark (FBL) is published by IMR Press from Volume 26 Issue 5 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.

Open Access Article
Receptor protein tyrosine phosphatases as mediators of cellular adhesion
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1 Department of Pharmacology and Neuroscience Program, University of Miami, Miami, Florida 33136, USA

Academic Editor: Michael Hortsch

Front. Biosci. (Landmark Ed) 2003, 8(4), 87–99; https://doi.org/10.2741/941
Published: 1 January 2003
(This article belongs to the Special Issue Neural cell adhesion molecules)
Abstract

Receptor protein tyrosine phosphatases (RPTPs) are structurally characterized by the diversity of their extracellular domains (ECDs). These domains display Ig-like, fibronectin type III (FNIII), MAM (meprin, A5, PTPmu), and carbonic anhydrase (CAH) motifs that resemble those present in many cell adhesion molecules (CAMs). However, in contrast to most CAMs, RPTPs also contain an intracellular domain possessing phosphatase activity. This combination makes RPTPs unusual in their ability to directly couple extracellular adhesion mediated events to intracellular signaling pathways. Even though identifying physiologically relevant ligands for RPTPs has proven difficult, recent experiments have shown that RPTPs can bind to themselves (homophilic) as well as to other proteins (heterophilic). For example, the type IIb RPTP, PTPmu? acts as a homophilic cell adhesion protein for epithelial and neural cells while the type V RPTP, PTPbeta/zeta binds a variety of CAMs and ECM components such as N-CAM and pleiotrophin. Interestingly, both PTPmu and PTPbeta/zeta interact with and regulate the tyrosine phosphorylation level of catenins, which are critical in physiological and pathological events such as cell migration, adhesion and transformation. In addition to their role as CAMs, RPTPs directly interact with intracellular adhesion regulators such as the cadherin/catenin complex, p130cas and GIT1. In summary, RPTPs represent a diverse family of transmembrane proteins that act as adhesion receptors and directly translate this engagement into intracellular signaling by modulating phosphotyrosine levels. Discovering the specific roles of RPTPs as receptors and identifying their ligands may lead to a better understanding of human illnesses whose underlying mechanisms involve cellular adhesion.

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