Measurement and computer modeling of temporary arrangements of polygonal actin structures in trabecular meshwork cells which consist of cross-linked actin networks and polygonal actin arrangements.
OBJECTIVE
In trabecular meshwork (TM) cells, actin geodesic arrangements were measured and then subjected to computational modeling to appreciate the response of different dome shapes to mechanical force.


METHODS
Polygonal actin arrangements (PAAs) and cross-linked actin networks (CLANs) were induced and imaged by Alexa Flour(®) 488 Phalloidin in bovine TM and human TM cells. Masked images were examined for size, circularity, and spoke and hub dimensions using ImageJ. Finite element modeling was used to create idealized dome structures and "realistic" PAA and CLAN models. The models were subjected to different loads simulating concentrated force and distortion measured.


RESULTS
We provide evidence that PAAs and CLANs are not identical. Both structures formed flattened domes but PAAs were 6 times larger than CLANs, significantly more circular and had greater height. The dimensions of the triangulations of hubs and spokes were, however, remarkably similar. Hubs were around 2 μm(2) in area, whereas spokes were about 5 μm in length. Our modeling showed that temporary arrangements of polygonal actin structures (TAPAS) were because of their flattened shape, more resistant to shearing than compression when compared with idealized domes. CLANs were marginally more resistant to shearing than PAAs but because of size much more resistant to compression.


CONCLUSIONS
Evidence is provided that there are 2 types of actin icosahedrons in cultured TM cells we collectively call TAPAS. Modeling suggests that TAPAS have rigidity and are better at dealing with shearing than compression forces. The 2 types of TAPAS, PAAs, and CLANs, have much in common but there are size and mechanical response differences that need to be taken into account in future experimentation.
1 Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, Faculty of Health and Life Sciences, University of Liverpool , Liverpool, United Kingdom .
Yalin
Y
Zheng
Laura
L
Currie
Natalie
N
Pollock
Andrew
A
Heath
Carl
C
Sheridan
Anshoo
A
Choudhary
Steven
S
O'Reilly
Ian
I
Grierson
D000199:Actins / Q000378:metabolism*; D000818:Animals; D051186:Armadillo Domain Proteins; D002417:Cattle; D002478:Cells, Cultured; D003198:Computer Simulation; D020342:Finite Element Analysis; D006801:Humans; D008954:Models, Biological; D015513:Oncogene Proteins; D014129:Trabecular Meshwork / Q000166:cytology*
C422103:ARMCX1 protein, human; D000199:Actins; D051186:Armadillo Domain Proteins; D015513:Oncogene Proteins