Solute carrier (SLC) membrane transport proteins control essential physiological functions, including nutrient uptake, ion transport, and waste removal. SLCs can be seen as gatekeepers and include over 400 membrane proteins arranged into 65 families based on sequence similarity. SLCs are the second-largest family of membrane proteins in the human genome.
SLCs are secondary active or facilitated transporters that translocate soluble molecules across cellular membranes. They can use ion gradients to drive uphill transports, work as exchangers, or facilitate passive diffusion of specific molecules. SLCs are vital for maintaining homeostasis in the body and in individual cells, and genetic polymorphisms in SLCs are associated with several diseases, such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease, and schizophrenia. Further- more, SLCs can function as drug targets, as well as constitute paths for drug absorption into specific organs.
Compared to other gene families of similar stature, SLCs are relatively understudied, with more than 30 % being orphan.
Consequently, the time is right for a systematic attack on SLC function, specificity, and regulation, taking into account kinship and expression, as well as the dependencies that arise from the common metabolic space.