The uncoupling protein homologues: UCP1, UCP2, UCP3, StUCP and AtUCP

Abstract

Animal and plant uncoupling protein (UCP) homologues form a subfamily of mitochondrial carriers that are evolutionarily related and possibly derived from a proton\anion transporter ancestor. The brown adipose tissue (BAT) UCP1 has a marked and strongly regulated uncoupling activity, essential to the maintenance of body temperature in small mammals. UCP homologues identified in plants are induced in a cold environment and may be involved in resistance to chilling. The biochemical activities and biological functions of the recently identified mammalian UCP2 and UCP3 are not well known. However, recent data support a role for these UCPs in State 4 respiration, respiration uncoupling and proton leaks in mitochondria. Moreover, genetic studies suggest that UCP2 and UCP3 play a part in

Differential expression of genes for uncoupling proteins 1, 2 and 3 in brown and white adipose tissue depots during rat development

“…Heat produced by BAT is required in special conditions such as birth and early development, at which time this tissue is well developed [1]. It is also known that there is an inability to appropriately thermoregulate with ageing due to a decrease in the number of b3-adrenergic receptors [39].…”

“…UCP1 is also induced by thyroid hormones (T3) [17], retinoid acid [18,19] and naturally occurring carotenoids [20]. The regulation of the new members of the UCP family, UCP2 and UCP3, is still not well known [1,4,21,22]. ucp2 seems to be regulated by diet, with increased expression when overeating, not being affected by shortterm cold exposure [5].…”

“…ucp3 regulation appears more similar to that of UCP1, as both are upregulated by cold exposure and downregulated by fasting in BAT [23]. Unlike UCP1, the functions of its homologues are currently unknown [1,21,22]. UCP2 and UCP3 have been implicated in lipid utilisation [24] or antioxidant mechanisms [25,26], but their relevance to body weight control has been argued.…”

Molekulare Grundlagen der Adipositas

“…Die im Rahmen der Substratoxidation gewonnene Energie wird mit Hilfe von UCP als Wärme freigesetzt, anstelle in Form von ATP konserviert zu werden [23]. Nach dem ausschließlich im braunen Fett vorkommenden UCP1 wurden mittlerweile drei weitere UCP identifiziert, wobei speziell das annähernd ubiquitär exprimierte UCP2 und das vorwiegend im Skelettmuskel nachweisbare UCP3 potentielle Kandidaten für eine wichtige Rolle im Rahmen des menschlichen Energiestoffwechsels sind.…”

Uncoupling proteins 2 and 3 and their potential role in human obesity

“…Unfortunately, these studies have not been very revealing regarding the regulation of either the function or the concentration of these proteins in the cells. Even though a large number of factors have been identified that can affect the level of either or both mRNAs, I will limit my review to those that seem more likely to be relevant to the problem of obesity and energy balance [see Ricquier and Bouillaud, 2000, for the latest comprehensive review].…”