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Rab7B/42 Is Functionally Involved in Protein Degradation on Melanosomes in Keratinocytes

Soujiro Marubashi1, Mitsunori Fukuda1

  • 1Laboratory of Membrane Trafficking Mechanisms, Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University.

Cell Structure and Function
|February 11, 2020
PubMed

Insights

Researchers identified Rab7B/42 as a key protein in keratinocytes that promotes the degradation of melanosomes. This discovery sheds light on how skin cells process these pigment structures, crucial for DNA protection.

Area of Science:

  • Cell Biology
  • Dermatology
  • Molecular Biology

Background:

  • Keratinocytes internalize melanosomes from melanocytes, forming melanin caps that protect nuclear DNA from UV damage.
  • The molecular mechanisms governing melanosome uptake and degradation within keratinocytes remain largely unknown.
  • A lack of specific markers hinders the visualization and study of internalized melanosomes in keratinocytes.

Purpose of the Study:

  • To identify molecular players involved in melanosome degradation within keratinocytes.
  • To investigate the role of Rab small GTPases in melanosome processing.
  • To establish a quantitative assay for assessing melanosome protein degradation.

Main Methods:

  • Comprehensive localization screening of mammalian Rab GTPases (Rab1-45).
  • Development of a novel assay using the M-INK melanosome probe.
  • Quantitative assessment of protein degradation on melanosomes in Rab-knockdown keratinocytes using CRISPR/Cas9.

Main Results:

  • Identified 11 Rab proteins enriched around internalized melanosomes in keratinocytes.
  • Demonstrated that Rab7B (also known as Rab42) is recruited to melanosome-containing compartments.
  • Showed that Rab7B/42 knockdown or knockout significantly inhibits melanosome protein degradation.

Conclusions:

  • Rab7B/42 plays a crucial role in promoting protein degradation on melanosomes within keratinocytes.
  • This finding provides insight into the molecular basis of melanosome processing in skin cells.
  • Rab7B/42 represents a potential target for understanding and modulating UV protection mechanisms.
Keywords:
Rab small GTPasedegradationkeratinocytesmelanocytesmelanosome

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