SLC6A4 and major depressive disorder: In two recent papers, we have shown that the pattern of clustering of two proteins (the serotonin transporter -SERT- and the serotonin 2A receptor -5HT2A-) in the plasma membrane of peripheral lymphocytes can differentiate two subpopulations of naïve depression patients that show a differential response to antidepressant treatment [11, 12].