Ama-amino acid ayizingxenye eziyisisekelo zamaprotheni kanye nezingxenye ezibalulekile zezicubu zomuntu, ezidlala indima yokudluliswa kwesignali yeseli, ukulawulwa komsebenzi wama-enzyme, umsebenzi wokuzivikela komzimba kanye neminye imisebenzi yomzimba.

Ubuningi bama-amino acid emangqamuzaneni ngokuvamile bushintsha ezimeni ezihlukahlukene ze-physiological and pathological. Ngakho-ke, indlela umzimba ozwa ngayo ukuguqulwa kwezinga le-amino acid nokwenza impendulo eguquguqukayo kuyinkinga ebalulekile yesayensi yokucindezeleka kwe-metabolic kanye nesiphetho samaseli.

Ukuzwa okungavamile kwe-amino acid kuhlobene eduze nomdlavuza, isifo sikashukela, izifo ze-neurodegenerative kanye nenqubo yokuguga. Ngakho-ke, ukuhlola indlela yamangqamuzana yokungeniswa kwe-amino acid engavamile kungase kunikeze ithagethi entsha yokuvimbela noma yokwelapha izifo ze-metabolic kanye nomdlavuza. I-Valine, njenge-amino acid ebalulekile ye-branched-chain, idlala indima ebalulekile ekuhlanganiseni amaprotheni, i-neurobehavior, kanye nokuqhubekela phambili kwe-leukemia. Kodwa-ke, indlela kanye nomsebenzi wokuzwa kwamaselula we-valine kusalokhu kungacacile.

Ngomhla zingama-20 kuNovemba, 2024, ithimba lika-Wang Ping lase-Tongji University School of Medicine / 10th Affiliated People's Hospital lishicilele iphepha locwaningo elinesihloko esithi "Human HDAC6 izwa ukuchichima kwe-valine ukuze ilawule ukulimala kwe-DNA" kumagazini i-Nature.

Lolu cwaningo luhlonze inzwa ye-valine ethize inoveli, i-deacetylase HDAC6 yomuntu, futhi lwembula indlela ethile lapho ukuvinjelwa kwe-valine kuholela ekudlulisweni kwe-nuclear ye-HDAC6, ngaleyo ndlela kuthuthukise umsebenzi we-TET2 nokudangala umonakalo we-DNA.

Kuyathakazelisa ukuthi le ndlela yokuzwa ihlukile ezinkambini, futhi ukuhlaziya okwengeziwe kwemishini kwembula ukuthi i-primate HDAC6 iqukethe isizinda esithile esiphindayo se-serine-rich glutamate-tetranectide (SE14) nomuzwa wobuningi be-valine ngalesi sizinda. Mayelana nokwelashwa kwesimila, ukuvinjelwa kwe-valine okumaphakathi noma inhlanganisela ye-PARP inhibitors kungavimbela ngempumelelo ukukhula kwesimila.

Lolu cwaningo luveza indlela entsha lapho ukucindezeleka kokudla okunempilo kulawula khona ukulimala kwe-DNA ngokuguqulwa kwe-epigenetic, futhi kuhlongoze isu elisha lokwelashwa kwesimila ngokudla okukhawulelwe kwe-valine okuhlanganiswe nama-PARP inhibitors.

Izinzwa ze-amino acid ngokuvamile zidinga ukuhlanganisa ama-amino acid ukuze zibone futhi ziphendule izinguquko ekugxilweni kwe-amino acid ngaphakathi nangaphandle kweseli, ukuze zenze umsebenzi wazo wokuzwa.

Ukuze kukhonjwe ngendlela ehlelekile amaprotheni abopha i-valine, ama-biotinylated valine probe asetshenziselwa ukuhlolwa kwe-immunocoprecipitate kuhlanganiswe ne-mass spectrometry, futhi ukuhlolwa okungachemile kwamaprotheni abopha i-valine kwenziwa yi-chemical biology.

Ababhali bathole ukuthi ngaphezu kwama-valyl tRNA synthetases (VARS) aziwayo, i-deacetylase HDAC6 ibonise amandla aqinile okubopha i-D-valine uma kuqhathaniswa ne-VARS. Ababhali baphinde baqinisekisa ukuthi i-HDAC6 ingabopha ngokuqondile i-valine ne-affinity ye-Kd ≈ 2μM ngokuhlolwa okubopha isotopu, ukuhlola kwe-isothermal titration calorimetry (ITC) kanye nokuhlolwa kwe-thermal drift. Ukuhlaziywa kwezici zesakhiwo sama-amino acid aqashelwa ngokuzwa amaprotheni kuyasiza ekuqhubekeleni phambili nokuqonda indlela yamangqamuzana yokushintsha kobuningi be-amino acid ebangelwa amaseli. Ngokuhlaziya uhlolo olubophezelayo lwama-analogue e-valine, ababhali bathola ukuthi i-HDAC6 ibona itheminali ye-carboxyl kanye nochungechunge oluseceleni lwe-valine futhi ingabekezelela ukuguqulwa kwetheminali ye-amino. Ukwengeza, kumaseli wokugoqa we-HDAC6, ukulawulwa kwendlela yokusayina ye-mTOR ngokuvinjelwa kwe-valine kwakungahlukanga kakhulu kulokho kweqembu elilawulayo, okuphakamisa ukuthi lokhu kubophezela kwakuhlukile endleleni evamile yokubonisa ukuzwa kwe-amino acid.

Ukuze uhlole isizinda esibalulekile kanye nomsebenzi we-valine yenzwa ye-HDAC6. Ababhali baphinde banquma ukuthi i-HDAC6 ibophezela i-valine ngesizinda sayo se-SE14 ngokuhlolwa kwe-HDAC6 okuncishisiwe kokubopha umzimba. Kuyamangaza ukuthi ababhali bathole ngokuqhathanisa i-homology ukuthi isizinda se-SE14 sitholakala kuphela ku-HDAC6 kuma-primates. Ngokungafani nenkawu (umuntu nemfene) HDAC6, igundane i-HDAC6 alibophezeli ku-valine. Lokhu kutholakala kwembula umehluko phakathi kwezinhlobo ezahlukene zezinhlobo zokungeniswa kwe-valine, okuphakamisa ukuthi ukuvela kwezinhlobo zezilwane kudlala indima ebalulekile ekungenweni kwe-amino acid.

Ngokusekelwe esiphethweni sokuthi i-HDAC6 ibophezela ngokuqondile i-valine ngesizinda sayo se-SE14, ababhali bacabange ukuthi izinguquko emandleni abophezelayo e-HDAC6 kanye ne-valine zingase zithinte ukwakheka nokusebenza kwayo lapho ukuchichima kwe-valine kumaseli kushintsha. Ngochungechunge lwezilingo futhi kuhlanganiswe nezincwadi ngendima ebalulekile yesizinda se-SE14 ekugcinweni kwe-cytoplasmic ye-HDAC6, abalobi bathola ukuthi ukuntuleka kwe-intracellular valine kungabangela ukudluliselwa kwe-HDAC6 ku-nucleus. I-enzyme esebenzayo yesifunda (i-DAC1 ne-DAC2) ibophezela endaweni esebenzayo (isizinda se-CD) se-DNA hydroxymethylase TET2, ikhuthaza ukuchithwa kwe-TET2, bese ivula umsebenzi wayo we-enzyme. Sisebenzisa amasu e-methylomics afana ne-WGBS, i-ACE-Seq ne-MAB-Seq, siphinde saqinisekisa ukuthi indlala ye-valine ye-intracellular ingakhuthaza i-DNA demethylation esebenzayo nge-axis yesignali ye-HDAC6-TET2. Ngaphambilini, ithimba lika-Andre Nussenzweig lathola ukuthi i-thymine DNA glycosylase (TDG) -i-DNA demethylation esebenzayo encike ku-DNA ibangele ukulimala komucu owodwa ku-neuronal enhancer. Ngokuhlanganisa i-TET2 ChIP-Seq nobuchwepheshe bokulandelana komphumela ophezulu END-Seq kanye ne-ddC S1 END-Seq, sinqume ukuthi ukushoda kwe-valine kukhuthaza ukulimala kwe-DNA. Ukulimala kwe-DNA okudalwe ukushoda kwe-valine nakho kuncike emonakalweni womucu owodwa odalwe ukukhishwa kwe-TDG kwe-oxymethylcytosine (5fC/5caC).

Sekuhlanganiswe ndawonye, ??ababhali bathola izinzwa ze-valine zenoveli futhi ngokokuqala ngqa bacacisa indlela yamangqamuzana lapho i-valine ikhawulela ukufakwa komonakalo we-DNA nge-axis yokusayina ye-HDAC6-TET2-TDG, okwengeza isici esisha ekuqondeni komsebenzi wokucindezelwa kwe-amino acid ekunqumeni isiphetho seseli.

Ukuvinjelwa kokudla noma ukuqondiswa kwe-amino acid metabolism kanye nokuzwa sekuyindlela ehambisanayo yokwandiswa kwempilo nokwelashwa kwezifo eziningi, kuhlanganise nomdlavuza. Njengoba kunikezwe ukuthi ukuncishwa kwe-valine kungabangela ukulimala kwe-DNA, ababhali baqhubeka baphenya ukuthi ukuvinjelwa kwe-valine kunendima yini ekwelashweni komdlavuza. Kumodeli yesimila somdlavuza we-colorectal xenograft, ukudla okufanele okukhawulelwe kwe-valine (0.41% valine, w/w) kunqande kakhulu ukukhula kwesimila ngemiphumela engemihle embalwa. Kuwo womabili amaqembu okuvimbela nokwelapha, ababhali baphinde bakhombisa ukuthi ukudla okukhawulelwe kwe-valine kuvimbela i-tumorigenesis nokuqhubekela phambili kusetshenziswa imodeli yomdlavuza we-colorectal PDX. Kumasampuli wesimila, amazinga e-valine anciphile ayehlotshaniswa kahle nokukhushulwa kokudluliselwa kwenuzi kwe-HDAC6, amazinga angu-5hmC, nokulimala kwe-DNA. Njengoba ukudambisa ukulimala kwe-DNA kuwukwelapha okulwa nomdlavuza, ngokomtholampilo kungenzeka ukuvimba ukulungiswa kwe-DNA ngokusebenzisa ama-PARP inhibitors. Ababhali bathole ukuthi inhlanganisela yokudla okukhawulelwe kwe-valine kanye ne-PARP inhibitor talazoparib iwuthuthukise kakhulu umphumela we-antitumor, inikeze ubufakazi obuqinile bokwelapha ukwelapha umdlavuza ngokudala umonakalo we-DNA.

Sengiphetha, ucwaningo lwathola ukuthi i-HDAC6 ezinkambini iyiprotheyini ekwazi ukuzwa i-valine inoveli ngaphandle kwezinzwa zendabuko, eveza umehluko wenzwa ye-valine phakathi kwezinhlobo ezahlukene zezilwane, okubonisa indima ebalulekile yokuvela kwezinto eziphilayo ekuzweni kwe-amino acid.

Ngaphezu kwalokho, lolu cwaningo lucacisa indlela entsha yokulawula okusebenzisanayo kokucindezeleka kwe-metabolic, ukulawulwa kwe-epigenetic kanye nokulimala kwe-DNA, kwandisa ukubaluleka kokucindezeleka okunomsoco ku-biology yokucindezeleka, futhi ithola ukuthi inhlanganisela yokudla okuvinjelwe i-valine kanye ne-PARP inhibitors ingasetshenziswa njengendlela entsha yokwelashwa komdlavuza.