Leptin or obesity receptor (Ob-R) is a ember of class I cytokine receptor family, Ob-R, expressed in six isoforms, is the product of alternative RNA splicing of db gene. According to its structural differences, the receptor’s isoforms are divided into three classes: long, short, and secretory isoforms. A long, fully active isoform of Ob-Rb is expressed mainly in the hypothalamus, where it takes part in energy homeostasis and in the regulation of secretory organs’ activity. Ob-Rb is also present on all types of immune cells, invovled in innate and adaptive immunity. Short leptin isoforms that contain box 1 motif are able to bind JAK kinases as well as to activate some other signal transduction cascades. A solube isoform can regulate serum leptin concentraiton and serve as a carreir protein delivering the hormone to its membrane receptors and is able to transduct the signal into the cell. (Wasik, “Leptin Recetpors” European Journal of Medical Research” 2010, 50-54).

A long, fully active isoform of Ob-Rb is epxressed mainly in the hypothalamus, where it takes part in energy, homeostasis, and int he regulation of secretory organs’ activity. Ob-Rb is also rpesent in all types of immune cells, involved in innate and adaptive immunity. (Wasik, “Leptin Recetpors” European Journal of Medical Research” 2010, 50-54).

Lack of a full-lenght Ob-Rb recetpor is responsible for the development of the early obesity phenotype in db/db mice and in obese rats. (Wasik, “Leptin Recetpors” European Journal of Medical Research” 2010, 50-54).

Short leptin isoforms that comtain box 1 motif are able to bind JAK kisnases and to activate some signal transduction cascades. However, the effect of short isoform activation differs from that of long isoform activation. Their main function is presumably connected with leptin internalization and degradation. A short isoform, Ob-Ra is the most common Ob-R isoform that can be found in many various cells and tissues, cinlduign kidney, lugns, liver, speen, and macroppages. (Wasik, “Leptin Receptors” European Journal of Medical Research” 2010, 50-54).

A major role in leptin signal transduction through membrane receptors is mediated through JAK/STATE pathway. Among all Ob-R isoforms, only the full lenght isoform is able to fully transduce and activaiton signal into the cell. Ob-Rb is considered a fully active receptor, because it contains 3 intracellular motifs necessary to activate the JAK/STATE pathway.