(Gene -cell news) Material Outside Of A Cell Can Move Into Cell Nucleus

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Material Outside Of A Cell Can Move Into Cell Nucleus More Easily

Than Previously Believed

http://www.medicalnewstoday.com/articles/79460.php

A team of Brooklyn College researchers has shattered a long-held

belief that no direct pathway exists between material outside of a

cell and the cell nucleus. (The cell is the smallest metabolically

functional unit of life.)

It was already known that material outside of a cell can migrate

into a cell. This occurs through processes known as endocytosis and

phagocytosis, in which extracellular material is captured by a

pinched-in segment of the cell membrane. This extracellular material

then becomes trapped inside the resulting membrane-bound

intracellular compartment, which is known as an endosome or

phagosome.

It was also already known that material can migrate out of an

endosome or phagosome and eventually enter the cell nucleus. But the

Brooklyn College team has discovered that a phagosome and its

contents can enter the cell's nucleus, where genetic information is

stored and processed.

The team's discovery of the existence of direct pathways between

extracellular material and cell nuclei will be published in Cell

Motility and the Cytoskeleton. The team was led by Ray Gavin and

funded by the National Science Foundation (NSF).

Gavin says that these newly discovered direct pathways mean

that " internalized material does not necessarily have to exit the

phagosome before entering the nucleus. " Therefore, his discovery

means that " one less step is needed for extracellular material to

get into the nucleus, and so it is far easier than previously

thought for this material to get into the nucleus. "

Eve Barak, an NSF program director, describes Gavin's discovery

as " an amazing and potentially paradigm-changing observation, " and

predicts that it " will have an enormous impact on how scientists

think about how cellular functions are regulated. "

Gavin has only observed direct pathways from the extracellular

environment to the nucleus in the one-celled protozoan Tetrahymena

thermophila. But Gavin says that " other discoveries that were based

on this protozoan were later shown to be almost global in their

occurrence in the biological world. " Therefore, these direct

pathways may operate in other organisms as well.

The discovery of the pathways in the protozoan resulted from an

observation made by Gavin about 10 years ago while simply watching

cells through a microscope. " I am a patient and constant observer of

living things, " he says. " And I watch them all the time with no

agenda in mind. Some people are window gazers. They stand in front

of the window and just look. I do the same with cells. "

During one of Gavin's agenda-less cell-watching sessions, he noticed

phagosomes clustered around a cell's nucleus. " It made me wonder why

the phagosomes were positioned in that way, " Gavin said. Thereafter,

Gavin periodically looked for this intriguing behavior again, and

occasionally glimpsed it again.

But Gavin remained unable to systematically search for phagosome

clusters around nuclei until he received NSF funding in 2006 to

purchase a confocal microscope, which provides three dimensional

views of the cell. Just like a person would eventually find a worm

hidden in an apple by repeatedly slicing through the apple, Gavin

found the intruiging phagosome behavior he sought by using the

confocal microscope to repeatedly obtain views that sliced clear

through the cell.

Specifically, the team tracked phagosomes carry extracellular

material into the cell nuceli by introducing fluorescent latex beads

into the area outside of the cell. They then observed the cells

phagocytose (eat) the beads, which gradually moved to the nucleus.

The arrival of the phagosomes and their loads at the nucleus was

marked by the illumination of the nucleus by the beads. Similarly,

the researchers also labeled the cellular membrane with a

fluorescent dye, and then observed the pinched off, internalized

membrane move to the nucleus.

" Biologists may now study the kinds of external molecules that can

gain entry to the nucleus through these newly defined pathways and

how these materials influence the nucleic material and its

processes, " said Gavin.