Pinocytosis

Pinocytosis is a form of endocytosis, a process by which cells absorb molecules (such as proteins) from outside the cell by engulfing it with their cell membrane. It is a type of phagocytosis that involves the intake of liquid into a cell via vesicles that are formed from the cell membrane.

Process

Pinocytosis is primarily used for the intake of extracellular fluids (ECF), and not for the intake of larger particles. The process involves the invagination of the cell membrane around the desired fluid or solute, forming a small vesicle. The vesicle then travels into the cell and fuses with endosomes and lysosomes to break down the contents.

Types

There are two types of pinocytosis: fluid-phase (non-specific) and adsorptive (specific).

• Fluid-phase pinocytosis is when the cell engulfs some of its extracellular fluid (ECF) containing dissolved substances, and is also known as "cell drinking".
• Adsorptive pinocytosis is when the cell intakes extracellular fluids through the use of specific binding proteins on the cell membrane.

Role in disease

Pinocytosis plays a role in many diseases, including cancer, atherosclerosis, and Alzheimer's. In cancer, pinocytosis can be used by tumor cells to intake nutrients from the extracellular fluid, allowing them to grow and multiply. In atherosclerosis, pinocytosis is used by cells in the artery wall to intake lipoproteins, leading to plaque formation. In Alzheimer's, pinocytosis is thought to be involved in the formation of amyloid plaques.

See also

• Endocytosis
• Phagocytosis
• Exocytosis
• Cell membrane

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