Amino Acid Sensing by Transceptors: Exploring Substrate-Induced Regulation of Amino Acid Transporters and Transporter Expression

Abstract

Adaptation to changes in environmental availability of nutrients such as amino acids is crucial for cellular survival. Given the requirement of amino acids as building blocks for proteins and their capacity to induce activation of the mTORC1 pathway, which plays a vital role in regulating protein synthesis and cell growth, amino acid sensing in mammalian cells is understandably critical for cellular maintenance, growth, and proliferation. Members of the System A amino acid (AA) transporter family play an important role in mediating the sodium (Na⁺) coupled uptake of short-chain neutral AAs into mammalian cells, but also exhibit the capacity to adapt their expression and function in response to changes in substrate availability reflecting a transceptor function [1]. Most of the well-studied amino acid transceptors are located within the plasma membrane, and therefore effective membrane isolation is an important element of transceptor investigation. Here, we outline interrogative methods to assess the amino acid and Na⁺-dependent regulation of System A (SNAT2) expression and activity. These methods have the capacity to be applied to other plasma membrane transporters/receptors.

Keywords: Amino acid transporter; Amino acid uptake; Immunoblot; Methyl aminoisobutyrate (Me-AIB); Plasma membrane; Sodium (Na+); Total cell membrane isolation.