Mechanism of receptor assembly via the pleiotropic adipokine Leptin

Abstract

The adipokine Leptin activates its type I cytokine receptor (LEP-R) in the hypothalamus to regulate body weight and exerts additional pleiotropic functions in immunity, fertility, and cancer. However, the structure and mechanism of Leptin-mediated LEP-R assemblies has remained unclear. Here, we show that Leptin:LEP-R assemblies adopt an unprecedented structure within the type I cytokine receptor family featuring 3:3 stoichiometry. We validate Leptin-induced trimerization of LEP-R in the plasma membrane of living cells via multicolor single molecule microscopy. In mediating such assemblies Leptin undergoes drastic restructuring that activates its site III for binding to the Ig-domain of an adjacent LEP-R molecule in the complex. These interactions are abolished by pathological mutations linked to obesity. Collectively, our study uncovers an evolutionarily conserved Leptin:LEP-R assembly as a new mechanistic blueprint for Leptin-mediated signaling in physiology and disease, including insights into how the lowly abundant signaling-competent isoforms of LEP-R can productively participate in signaling.

Rare Antagonistic Leptin Variants and Severe, Early-Onset Obesity

“…Complexities of receptor binding and activation mechanisms may have also contributed to the observed differences. 15,27 Collectively, these results show that leptin variants P64S and G59S behave as competitive LEPRb antagonists in the presence of nonvariant leptin, while retaining faint partial agonist activity in its absence.…”

“…[11][12][13][14] Leptin features three interaction sites (IS-I, IS-II, and IS-III) through which it engages the leptin receptor, forming an active oligomeric complex. 15 IS-II and IS-III are critical for the bioactivity of leptin. [16][17][18][19] IS-II is formed by residues of helixes A and C and mediates high-affinity binding to the second cytokine-receptor homology domain (CRH2) of one LEPRb chain to establish an initial leptin-LEPRb complex.…”

“…[20][21][22] IS-III comprises the AB loop and parts of helix D and subsequently partakes in a low-affinity interaction with the immunoglobulin-like domain (IGD) of another LEPRb chain to induce conformational changes in the complex, causing its activation. 15 Afterward, additional LEPRb chains may also be recruited to the complex. 15 which is composed of six questions (e.g.…”

“…15 Afterward, additional LEPRb chains may also be recruited to the complex. 15 which is composed of six questions (e.g. "How strong is your desire to eat?")…”

Tuning of granulopoietic signaling byde novodesigned agonists

“…To this end, G-CSFR fused to an N-terminal ALFA-tag was expressed in HeLa cells and labeled selectively at the cell surface by applying a mixture of anti-ALFA nanobodies conjugated with Cy3B and AT643, respectively (Fig. 4A) [51]. Since it has been shown, that associated JAK2 energetically contributes to cytokine receptor complex formation, we additionally transfected JAK2 C-terminally fused to mEGFP [8].…”