Transporter explosion: update on uptake

Transporter explosion: update on uptake Transporter genes encode proteins, most with proposed 12 transmembrane region topologies, which usually mediate Na+-or H+-dependent accumulation of small molecules into cells or organelles and represent one of the most explosively developing areas of membrane molecular biologyl.Neurotransmitter and vesicular transporters reaccumulate released neurotransmitters into presynaptic terminals and vesicles, aiding termination of synaptic transmission and recycling of neurotransmitters.These transporters represent sites of action of several important drug classes, including antidepressant medications and psychostimulants such as cocaine.A meeting* of workers from laboratories involved in this burgeoning field captured a snapshot of work describing the rapidly maturing molecular biological, pharmacological and functional analysis of these new gene family members, and revealed emerging general principles of family organization and function (Fig. 1). Na+/Cl--dependent neurotmnsmitter transportersTransporters can now be classified into families and subfamilies based on ion dependence, topology, and sequence relatedness (Fig. 1).Much attention focused on members of the Na+-(and Cl--) dependent neurotransmitter transporter (plus) family that is of key importance for neurotransmitter uptake1 (Fig. 1).This family can be divided into monoamine-recognizing and amino acid-like subfamilies, based on overall sequence homologies and on possession of specific amino acid residues such *Held on 10 and 11 August 1992, in Bethesda, MD, USA under the auspices of the Medications Development Division, Division of Preclinical Research, and Addiction Research Center of the National Institute on Drug Abuse: The molecukr neurobiology of neurotransmitter and related transporters: structure, expression, function, and lessons for treating cocaine abuse'.as a first transmembrane region aspartic acid (see later). Monoamine subfamilyThe monoamine subfamily consists of single dopamine, noradrenaline and 5-HT transporter genes identified to date.Diversity within this subfamily can occur in several fashions.Alternative poly(A+)-site usage appears to generate heterogeneity in the mRNAs encoding noradrenaline and human 5-HT.transporters, as described by S.