Dinamika GTPaza Rac1 i njihova uloga u regulaciji polarnosti stanica Dictyostelium discoideum

doctoral thesis

• Title (english): Dynamics of Rac1 GTPases and their role in the regulation of cell polarity in Dictyostelium discoideum
• Author: Maja Marinović
• Mentor: Igor Weber (mentor)
• Committee member: Maja Osmak (član povjerenstva)
• Committee member: Maja Herak Bosnar (član povjerenstva)
• Committee member: Renata Matoničkin Kepčija (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2015, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology
• Universal decimal classification (UDC): 576 - Cellular and subcellular biology. Cytology

Abstract

Proteini Rac su jedini predstavnici obitelji malih GTPaza Rho u organizmu Dictyostelium discoideum. Rezultati dosadašnjih istraživanja ukazuju na dvojaku ulogu Rac1 u regulaciji polimerizacije aktina, koja je ključna odrednica stanične polarnosti. Osim što na prednjem kraju stanice aktivacijom kompleksa Scar/WAVE potiče polimerizaciju aktina posredovanu kompleksom Arp2/3, Rac1 istodobno regulira stabilnost stražnjeg kraja kao inicijator stvaranja kompleksa jednog od IQGAP proteina, DGAP1 ili GAPA, s heterodimerom korteksilina. Kako bi dobili detaljniji uvid u funkcije tri izoforme proteina Rac1 iz D. discoideum, Rac1A, 1B i 1C, konstruirali smo poboljšanu probu koja je specifična za aktivni oblik GTPaze Rac1, a sastoji se od domene GBD iz proteina DPAKa fuzionirane sa žutim fluorescentnim proteinom. Praćenjem lokalizacije probe DPAKa_GBD-DYFP, kao i njene kolokalizacije s probama za druge proteine relevantne za organizaciju aktinskog citoskeleta, dobili smo uvid u vremensko-prostorne odnose glavnih komponenti ovog dinamičnog sustava u živim stanicama. Osim toga, analiza mutanta deficijentnog za dvije izoforme Rac1, 1B i 1C, pokazala je da, unatoč velikoj međusobnoj sličnosti, tri izoforme proteina Rac1 nemaju potpuno preklapajuće funkcije u stanicama D. discoideum.

Abstract (english)

Rac proteins are the only members of the Rho family of small GTPases present in Dictyostelium discoideum. It has been shown that Rac1 proteins play a dual role in the regulation of actin polymerization, which is the key determinant of cell polarity. At the front end of a cell Rac1A activates the Scar/WAVE complex and stimulates Arp2/3-mediated actin polymerization, while it simultaneously regulates stability of the rear end by initiating formation of a complex containing one of the IQGAP-related proteins, DGAP1 or GAPA, and the cortexillin heterodimer. To gain more insight into the roles of three highly homologous Rac1 proteins in D. discoideum, Rac1A, 1B and 1C, we developed an improved probe for active Rac1 GTPases. The probe consists of the GBD domain from DPAKa fused with the yellow fluorescent protein. We monitored localization of the DPAKa_GBD probe, and it's colocalization with probes for other proteins involved in organization of the actin cytoskeleton, to obtain information about spatio-temporal relations between main components of this dynamic system in live cells. Functional analysis of D. discoideum Rac1B/1C-deficient strain revealed that, although three Rac1 proteins are highly homologous, their roles are not completely redundant.

• Keywords: GTPaze Rho; Rac1; aktinski citoskelet; stanična polarnost; Dictyostelium
• Keywords (english): Rho GTPases; Rac1; actin cytoskeleton; cell polarization; Dictyostelium
• Language: croatian
• URN:NBN: urn:nbn:hr:217:042354
• Study programme: Title: Biology; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje prirodnih znanosti, polje biologija (doktor/doktorica znanosti, područje prirodnih znanosti, polje biologija)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2017-05-17 09:24:44