During hypoxia, HUMMR joins the mitochondrial dance

Area of Science:

• Cell Biology
• Neuroscience
• Mitochondrial Dynamics

Background:

• Mitochondrial distribution is crucial for cellular functions, especially in highly polarized cells like neurons.
• Proper mitochondrial transport is essential for synaptic function, neurite plasticity, cellular migration, and calcium signaling.
• Proteins like Miro and Milton mediate mitochondrial transport by tethering them to kinesin motor proteins.

Purpose of the Study:

• To identify novel proteins involved in mitochondrial transport and distribution.
• To investigate the role of the newly identified protein, HUMMR, in mitochondrial movement, particularly under hypoxic conditions.

Main Methods:

• Identified HUMMR, a novel protein interacting with Miro on the outer mitochondrial membrane.
• Analyzed HUMMR protein abundance under normoxia and hypoxia, noting its induction via a HIF-1 dependent mechanism.
• Performed knockdown experiments of HUMMR function in neurons, assessing mitochondrial distribution and movement (anterograde/retrograde) under normoxic and hypoxic conditions.

Main Results:

• HUMMR protein abundance is significantly increased under hypoxia through a HIF-1 dependent pathway.
• Knockdown of HUMMR reduces the number of mitochondria in neuronal axons, with a more pronounced effect under hypoxia.
• In hypoxic neurons, HUMMR knockdown decreases anterograde mitochondrial movement while increasing retrograde movement, indicating a bias towards anterograde transport.

Conclusions:

• HUMMR acts as a key regulator biasing mitochondrial movement in the anterograde direction, especially in response to hypoxia.
• HUMMR's role in mitochondrial distribution is significant under hypoxic conditions, relevant to ischemia and solid tumors.
• Further research is needed to determine the implications of HUMMR-mediated mitochondrial transport on neuronal function and viability during hypoxia.