May  6,  2015
In  their  latest  study,  Alwin  Köhler  and  his  team  from  the  Max  F.  Perutz  Laboratories  (MFPL)  of  the  University  of
Vienna  and  the  Medical  University  of  Vienna  give  new  insights  into  how  nuclear  pores  are  formed  in  the  envelope   of  cell  nuclei.  Nuclear  pores  are  molecular  gates  that  allow  controlled  exchange  of  cargo  between  the  nucleus  and   the   cytoplasm   of   eukaryotic   cells.   This   exchange   is   vital   and   errors   are   associated   with   cancer,   aging   and   autoimmune  diseases.  The  findings  are  published  online  today  in  the  scientific  journal   Developmental  Cell .
Cells  are  the  building  blocks  of  life:  around  100  trillion  make  up  a  human  being,  while  other  organisms  such  as  bacteria   consist  of  a  single  cell.  Organisms  are  broadly  divided  into  two  categories:  those  containing  a  nucleus  –  the  eukaryotes
–  and  those  without  –  the  prokaryotes  –.  All  higher  life  forms  such  as  humans  and  animals  are  eukaryotes  and  their   defining  feature  is  an  organelle  that  encapsulates  and  protects  their  genetic  material:  the  nucleus.
The   nucleus   is   surrounded   by   a   double   membrane,   which   separates   it   from   the   rest   of   the   cell.   Quite   similar   to   a   medieval  town  surrounded  by  two  walls.  Just  as  it  is  important  for  the  people  living  in  that  town  that  goods  and  food   are  transported  in  and  out  of  the  city,  a  controlled  exchange  of  molecules  between  the  nucleus  and  the  cytoplasm  is   vital   for   cells.   Gates   in   the   town   wall   are   what   nuclear   pores   are   to   the   nucleus.   These   extremely   large   protein   complexes  form  a  selective  channel  that  spans  the  entire  nuclear  membrane.  On  the  inside  of  the  nucleus  this  channel   extends  into  the  "nuclear  basket",  a  structure  that  indeed  resembles  a  basketball  basket.
Understanding  the  structure  and  function  of  this  "nuclear  basket"  is  a  research  focus  of  ERC-­‐  and  START  Prize  winner
Alwin  Köhler  and  his  team  at  the  Max  F.  Perutz  Laboratories  of  the  Medical  University  of  Vienna.  "Until  now,  everyone   assumed   that   the   basket’s   main   function   is   that   of   a   docking   site   for   cargo   transport.   However,   when   we   overexpressed  basket  proteins,  meaning  we  made  the  cell  produce  far  too  much  of  it,  we  saw  dramatic  changes  in  the   structure   of   the   nucleus.   The   nuclear   membrane   was   massively   deformed   when   compared   to   its   normal   spherical   shape,"  said  Alwin  Köhler.  This  initial  observation  led  the  researchers  to  investigate  whether  basket  proteins  have  an   ability  to  directly  shape  nuclear  membranes.
To  build  a  new  nuclear  pore,  the  double  membrane  of  the  nucleus  needs  to  be  reconstructed  to  allow  the  formation   of  a  "hole”.  To  achieve  this,  the  two  nuclear  membranes  must  approach  each  other,  bend  sharply  and  finally  merge.
PhD  student  Noémi  Mészáros  explains:  "It's  as  if  you  fold  a  section  of  the  outer  town  wall  inwards  and  a  section  from   the  inner  wall  outwards  to  create  an  opening  for  building  a  new  gate."  Colleague  and  joint  first  author  of  the  study
Jakub  Cibulka  adds:  "Our  experiments  showed  that  the  basket  proteins  can  deform  membranes  even  in  a  test  tube.
Moreover,  nuclear  membranes  lacking  the  basket  proteins  became  unstable  in  cells  and  formed  abnormal  membrane   structures  instead  of  proper  holes"  Taken  together,  these  results  confirmed  the  initial  assumption  of  the  researchers   that  basket  proteins  are  more  than  just  docking  sites  for  transport.  Rather,  they  actively  help  to  shape  the  nuclear   membrane  so  that  a  new  nuclear  pore  can  be  formed.
These  findings  may  help  researchers  to  better  understand  how  an  amazingly  complex  molecular  gate  is  constructed   and   on   the   long   run   what   happens   when   it   deteriorates   in   cancer   and   aging.   Alwin   Köhler   and   his   team   are   now   attempting  to  understand  the  general  principles  of  nuclear  membrane  (re)construction,  for  which  this  study  was  just   the  beginning.  "This  project  shows  once  again  that  biology  always  holds  surprises  and  that  basic  research  can  not  be   totally   planned.   Without   long-­‐term   funding   by   the   ERC,   the   Austrian   Science   Fund   FWF   and   the   Human   Frontier
Science  Program  this  project  would  not  have  been  possible,"  concludes  Alwin  Köhler.
MAX  F.  PERUTZ  LABORATORIES
Vienna  Biocenter  (VBC,)  Dr.  Bohr-­‐Gasse  9  |  1030  Wien  |  Austria
Tel:  +43  1  4277  24014     communications@mfpl.ac.at  |  www.mfpl.ac.at
The  Max  F.  Perutz  Laboratories  are  a  joint  venture  of

Publication  in   Developmental  Cell:
Noémi  Mészáros,  Jakub  Cibulka,  Maria  Jose  Mendiburo,  Anete  Romanauska,  Maren  Schneider  &  Alwin  Köhler:   Nuclear   pore  basket  proteins  are  tethered  to  the  nuclear  envelope  and  can  regulate  membrane  curvature.
In:  Developmental  Cell  (May  2015)
DOI:   http://dx.doi.org/10.1016/j.devcel.2015.02.017
Online  Press  Release:   http://www.mfpl.ac.at/about-­‐us/press-­‐media-­‐info/pressdetail/news-­‐detail/nuclear-­‐membrane-­‐reconstruction-­‐how-­‐ to-­‐make-­‐a-­‐proper-­‐hole-­‐in-­‐the-­‐wall.html
Press  contact
Dr.  Lilly  Sommer
Max  F.  Perutz  Laboratories
Communications
T  +43-­‐1-­‐4277-­‐240  14   lilly.sommer@mfpl.ac.at
The  Max  F.  Perutz  Laboratories  (MFPL)  are  a  center  established  by  the  University  of  Vienna  and  the  Medical  University   of  Vienna  to  provide  an  environment  for  excellent,  internationally  recognized  research  and  education  in  the  field  of
Molecular  Biology.  On  average,  the  MFPL  host  60  independent  research  groups,  involving  more  than  500  people  from
40  nations.
Page  2
The  Max  F.  Perutz  Laboratories  are  a  joint  venture  of

How  nuclear  pore  complexes  assemble  and  insert  into  the  nuclear  envelope  is  still  an  enigmatic  process.  Mészáros  et   al.  describe  how  amphipathic  helices  of  the  nuclear  pore  basket,  a  structure  on  the  nucleoplasmic  side  of  the  pore,  can   generate  highly  curved  membranes  to  promote  nuclear  pore  assembly.  The  image  shows  an  electron  micrograph  of  a
S.cerevisiae  cell.  Drawing  follows  the  contour  of  a  dramatically  remodeled  nuclear  envelope,  a  pathological  condition   seen  upon  overproduction  of  basket  amphipathic  helices  (yellow  cog  wheels),  which  bind  and  bend  membranes.
Artwork  by  Davor  Markovic.
Page  3
The  Max  F.  Perutz  Laboratories  are  a  joint  venture  of