Arginine transport in human monocytic leukemia THP-1 cells during macrophage differentiation

Abstract

L-arginine metabolism in myeloid cells plays a central role in the processes of macrophage activation and in the regulation of immune responses. In this study, we investigated arginine transport activity and the expression of the related transporter genes during the differentiation of monocytes to macrophages. We show here that the induction of THP-1 monocyte differentiation by PMA markedly increases the expression of SLC7A7 mRNA and of y ϩ LAT1 protein and consequently, the activity of system y ϩ L-mediated arginine transport. Conversely, the activity of system y ϩ decreases during macrophage differentiation as a result of a reduction in CAT1 protein expression. The PMA-induced, macrophage-differentiated phenotype and the increased activity of system y ϩ L through the induction of SLC7A7 gene are mediated by the specific activation of PKC␤. SLC7A7 gene silencing causes a significant reduction of system y ϩ L activity and a subsequent, marked increase of arginine and lysine cell content, thus suggesting that in macrophagic cells, system y ϩ L activity is mainly directed outwardly. Differentiating agents other than PMA, i.e., VD3 and ATRA, are equally effective in the stimulation of system y ϩ L transport activity through the increased expression of SLC7A7 mRNA and y ϩ LAT1 protein. Moreover, we found that also during differentiation of human monocytes from peripheral blood SLC7A7 mRNA and system y ϩ L activity are increased. These findings point to SLC7A7 gene as a marker of macrophage differentiation. J. Leukoc. Biol. 90: 293-303; 2011.

Inhaled Sargramostim Induces Resolution of Pulmonary Alveolar Proteinosis in Lysinuric Protein Intolerance

“…Toll-like receptor signalling, especially a response to viral DNA, has been shown to be impaired, and nitric oxide (NO) production decreased in LPI monocyte-derived macrophages reinforcing the role of macrophages in the development of secondary complications of LPI (Kurko et al 2015). We hypothesized that, in contrast to the earlier suggestions by other groups (Sebastio et al 2011;Ogier de Baulny et al 2012), arginine reservoirs and the subsequent NO levels may actually be diminished in LPI macrophages as a result of reduced arginine influx by the defective y + LAT1 transporter, known to be the most important transporter of arginine in macrophages, including those of alveolar origin (Barilli et al 2011;Rotoli et al 2007). In addition, the defective CAA transport also results in impaired phagocytic activity of LPI macrophages (Barilli et al 2012).…”

The SLC7A7 Transporter Identifies Microglial Precursors prior to Entry into the Brain

“…Interestingly, it has been shown that an increase in Slc7a7 expression and Arginine transport is characteristic of human monocyte differentiation into macrophages in vitro. Knocking down Slc7a7 in monocytes leads to Arginine accumulation in these cells (Barilli et al, 2011).…”

Arginine dependence of acute myeloid leukemia blast proliferation: a novel therapeutic target

“…The role of the CAT family of proteins in hematopoiesis has only received limited study, identifying CAT-1 and CAT-2B as the main transporters responsible for arginine uptake in in vitro models of nonmalignant myeloid and erythroid cells. [34][35][36] Arginine can be produced within healthy cells, by the ornithinecitrulline-arginine cycle. 37,38 We identified that the majority of patients' blasts are deficient in either ASS or OTC enzymes, strongly suggesting that AML blasts are reliant on extracellular arginine availability.…”