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[EU] Proteinak polimero lineal gisa sintetizatzen dira eta beren jatorrizko egitura tridimentsionalean tolestu behar dira zelulan hainbat funtzio betetzeko. Proteinen tolespena ulertzea funtsezkoa da, tolespen okerrak hainbat gaixotasun neuro-degeneratiboren jatorria direlako. Proteinen tolespena modu koitzultzailean has daiteke, hau da, sortzen ari den peptidoa erribosomari lotuta dagoenean oraindik. Izan ere, zelularen proteinen heren bat baino gehiago erribosomaren tunelaren espazio mugatuan tolesten direla frogatu da, hau da, erribosomaren gainazalarekiko interakzioek modulatuta eta erribosoma-tunelaren beraren mugen pean. Gero eta ebidentzia gehiagok iradokitzen dute erribosomak funtsezko zeregina duela proteinen tolespenean. Erribosomak proteina trinkotzea erraztu dezake, soluzioan ikusten ez diren bitartekoak sortzea eragin dezake edo tolestearen hasiera atzeratu dezake. Hala ere, proteinen koitzulpenezko tolesdura aztertzeak zailtasun handiak ditu, batik bat, egungo teknikek dituzten mugengatik. Hori dela eta, proteinen tolesteari buruzko ikerketa gehienak soluzioan dauden proteinetan oinarritzen dira, proteina tolestuz eta destolestuz egiten direnak, prozesu horretan erribosomak duen rola kontuan hartu gabe. Artikulu honetan, azken urteotan proteinen koitzulpenezko tolestura ikertzeko garatu diren tekniken laburpena egin da., [EN] Proteins are synthesised as linear polymers and must fold into their native three-dimensional structure to perform various functions in the cell. Understanding protein folding is crucial because protein misfolding is at the origin of several neurodegenerative diseases. Protein folding can start co-translationally, i.e. when the emerging peptide is still associated with the ribosome. Indeed, it has been shown that more than one third of the cell’s proteins fold in the limited space of the ribosome tunnel. Increasing evidence suggests that the ribosome plays a critical role in protein folding. The ribosome can facilitate protein compaction, cause the creation of non-visible media in solution or delay the onset of folding. However, the study of co-translational folding presents serious difficulties, mainly due to the limitations of the different current techniques. Hence, most studies on protein folding are based on proteins in solution, which are carried out by unfolding and refolding the protein, without taking into account the role of the ribosome in this process. In this article, we summarised the techniques developed in recent years for the study of co-translational protein folding.

SK channels, widely expressed in excitable cells, contribute to the after-hyperpolarization following an action potential, mediate the intrinsic excitability of neurons, and control resting potential in lymphocytes and erythrocytes. Ca2+ gates their activity via calmodulin, which is bound at the C-terminus. These channels are targets of riluzole, the only known treatment for amyotrophic lateral sclerosis (ALS), which has limited effectiveness. This drug increases the efficacy of Ca2+ to open the channel. Thus, finding new drugs with improved pharmacology with a similar mode of action is of utmost interest. However, the methodology to assess Ca2+ sensitivity by current electrophysiological methods represents a bottleneck for screening programs. An alternative is creating simplified systems, devoid of most of the protein components, amenable to other techniques. The challenge is to capture the main molecular events that take place during activation yet preserving the same pharmacological profile. The aim of this work is to design biosensors based on the SK4 channel gating that recent cryoEM studies have revealed. Based on these structures, we predicted that upon Ca2+ biding, two regions of the structure should come in close proximity, a movement amenable for detection by FRET. However, this first generation of rationally designed biosensors responded in the opposite direction, with a very small signal to noise ratio. After a fresh new redesign, and several phases of optimization, we have obtained a biosensor template that recapitulates the response to Ca2+ and riluzole observed in the full channel. In addition, we have designed a new library of riluzole analogues oriented by structural bioinformatic approaches. These new biosensors could provide a fast, cheap and effective platform for new therapeutic drug screening.

Protein co-translational missfolding lead to diseases, such as Alzheimer or Parkinson, but little is known about the role of ancillary proteins. We have demonstrated for the first time that the co-translational folding assistance by calmodulin (CaM) to the KV7.2 channel Calcium Responsive Domain (CRD) is disrupted in epileptogenic encephalopathy.1 The force exerted during the early folding events of the nascent chain can be assessed with single residue resolution. We describe here the force profile of folding of the CRD during translation. We find that CaM, the most important calcium modulator in eukaryotic cells, is required to generate early folding events on this domain at critical places. This investigation provides new insights into how a critical KV7.2 channel domain acquires its final functional conformation during co-translational synthesis.

Kaltzioa seinalizazio unibertsaleko mezulari bat da, funtsezko prozesuetan parte hartzen duena, hala nola apoptosian, zelulen proliferazioan eta muskuluen uzkurduran. Prozesu horietan parte hartzen duten proteina askok ioi honen kontzentrazioari erantzuteko kaltzio sentsore batekin, kalmodulinarekin (CaM), elkarreragin behar dute. Horrek ehunka proteinaren aktibitatea erregulatzen du bere N- eta C-lobuluen bidez, non EF-eskuak aurkezten dituen Ca2+-ari lotzeko. Zelulen seinalizazioan CaM-k duen papera hedatuta dagoen arren, haren mutazioek bereziki bihotzari eragiten diote. Izan ere, CaM proteina berdinak kodetzen dituzten hiru geneetako edozeinetan gaixotasunak eragiten dituzten mutazioek bihotz-disfuntzio larriak eragiten dituzte, eta horrek kitzikagarritasunaren erregulazioan duen garrantzia adierazten du. Beraz, esku hartzen duten mekanismoen ezagutzak aukera eman dezake adierazpen klinikoei modu kritikoan heltzeko eta kalmodulinopatietarako estrategia terapeutikoak garatzen laguntzeko., Calcium is a universal signaling messenger that participates in essential processes such as apoptosis, cell proliferation and muscle contraction. Many of the proteins involved in these processes must interact with a calcium sensor to respond to the changes of concentration of this ion. The best-studied sensor is Calmodulin (CaM). It regulates the activity of hundreds of proteins through its N- and C- lobes, where two EF-hands are located to bind up to four calcium ions. Although the role of CaM in cell signaling is widespread, its mutations are especially recognized through its effects on cardiac function. In fact, disease-causing mutations in any of the three genes that encode the same CaM proteins cause severe cardiac dysfunction, indicating their importance in regulating excitability. Therefore, knowing the mechanisms involved in these diseases can allow a rational approach to clinical manifestations and contribute to the development of therapeutic strategies.