The key difference between lamellipodia and filopodia is that the lamellipodia are cytoskeletal actin projections present in the mobile edges of the cells while filopodia are thin cytoplasmic protrusions that extend from the leading edge of the mobile cells.
Lamellipodia and filopodia are two cellular extensions commonly used in cell probing and migration. These structures sense the extracellular conditions and locomote respectively. Hence, they are essential structures for cell mobility. Also, microspikes refer to these lamellipodia and filopodia, and compose actin filaments. Both structures are present on the leading edge of a migrating cell.
CONTENTS
1. Overview and Key Difference
2. What is Lamellipodia
3. What is Filopodia
4. Similarities Between Lamellipodia and Filopodia
5. Side by Side Comparison – Lamellipodia vs Filopodia in Tabular Form
6. Summary
What are Lamellipodia?
Lamellipodia are cytoskeleton protrusions in the flat ribbon-shape and present at the periphery of a migrating cell. These protrusions are enriched with a branched network of bi-dimensional dendric array of actin filaments. In other terms, a lamellipodium contains a two-dimensional actin mesh which propels the whole cellular structure across a substrate. Therefore, they are extremely vital for cell migration.
Figure 01: Lamellipodium and Filopodium
Lamellipodia work like motors and pull the cells forward during cell migration. Hence, it is a characteristic feature present at the leading front edge of motile cells. Lamellipodia are primarily present in keratinocytes of fish and frogs, which allow them to move over epithelial surfaces at speeds of 10-20 μm/min. Even if the lamellipodia separate from the cell, they still have the ability to move on its own, freely.
What are Filopodia?
Filopodia are membranous cytoplasmic protrusions present in a cell to probe the extracellular environment. Hence, they act as antennas. Filopodia are thin protrusions generally present in the free end of migratory tissues embedded within or extending from the lamellipodium. These protrusions are commonly present in the growth cones of neurons, protruding end of migratory cells, epithelial sheets and in individual cells such as fibroblasts.
Figure 02: Filopodia
Filopodia contain actin filaments arranged in parallel bundles with a diameter of 60-200 nm. Hence, each filopodium contains 10-30 actin filaments. Also, binding proteins such as fascin and fimbrin hold these actin filaments together. The orientation of these filaments occurs so that the barbed ends are directed towards the extending membrane. The distal end of each filopodium contains cell surface receptors. These receptors act as sensors to probe the external environment. The assembly of filopodia contains three basic steps: filament nucleation, sustained barbed end elongation, and filament bundling.
What are the Similarities Between Lamellipodia and Filopodia?
- Lamellipodia and filopodia are made up of actin filaments.
- Also, both structures are present on the leading edge of migrating cells.
- Both lamellipodia and filopodia sense the extracellular environment and help in cellular migration.
What is the Difference Between Lamellipodia and Filopodia?
Lamellipodia are cytoskeletal protein actin projections that occur at the leading edge of the migratory cells. Whereas, filopodia are slender cytoplasmic projections that extend beyond the leading edge of lamellipodia in migrating cells. Therefore, this is the key difference between lamellipodia and filopodia. Furthermore, lamellipodia are highly specialized for cell migration while filopodia are specialized for sensing the external environment. Hence, we can consider this also as a difference between lamellipodia and filopodia.
The below infographic summarizes the difference between lamellipodia and filopodia.
Summary – Lamellipodia vs Filopodia
Lamellipodia and filopodia are two extensions present in the leading edges of migratory cells. Both contain actin filaments. However, lamellipodium is a cytoskeletal extension but, filopodium is a cytoplasmic extension. Hence, this is the key difference between lamellipodia and filopodia. Moreover, even though both extensions help in cell migration, filopodia can probe the extracellular environment. Whereas, lamellipodia are highly specialized for cell migration. In fish and frog, the lamellipodia are present in the keratinocytes. Thus, this is a summary of the difference between lamellipodia and filopodia.
Reference:
1. “Lamellipodium.” NeuroImage, Academic Press, Available here.
2. “What Are Filopodia?” MBInfo, Available here.
Image Courtesy:
1. “GrowthCones” By Chris1387 (talk) – self-made (CC BY-SA 3.0) via Commons Wikimedia
2. “Filopodia” By Lubov Czech, Tatyana Svitkina, and Changsong Yang – PLoS Biology Featured Image, Vol. 5(11) November 2007. (CC BY 2.5) via Commons Wikimedia
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