In a neuron, proteins and membranes are primarily synthesized in the cell body. These materials must be transported down the axon to the synaptic region using microtubules in an anterograde fashion. Such axonal transport is directed by
Kinesin I
Axonal Transport Direction
Neurons are highly specialized cells with a cell body, an axon, and synapses. The cell body is where many essential components like proteins and membranes are synthesized. These components are needed throughout the neuron, including at the distant synaptic terminals. Therefore, there is a constant need to transport these materials from the cell body down the axon towards the synapse. This movement is called anterograde axonal transport.
This transport system relies on the cytoskeleton of the neuron, specifically microtubules, which act as tracks or pathways along the axon. Motor proteins bind to the cargo (like vesicles containing proteins or membrane components) and move them along these microtubule tracks.
There are different types of motor proteins involved in axonal transport, and they move cargo in specific directions:
- Anterograde transport: Movement away from the cell body towards the synapse.
- Retrograde transport: Movement towards the cell body from the synapse.
The question asks which motor protein directs the anterograde axonal transport of proteins and membranes synthesized in the cell body down the axon to the synaptic region using microtubules.
Motor proteins that walk along microtubules belong primarily to two families: kinesins and dyneins.
Kinesin proteins are generally responsible for anterograde transport. They typically move towards the plus end of the microtubule, which in axons points away from the cell body towards the synaptic terminal. Kinesin I is a well-known member of the kinesin family and is a primary motor protein for fast anterograde axonal transport.
Dynein proteins are generally responsible for retrograde transport. They typically move towards the minus end of the microtubule, which in axons points towards the cell body.
Myosin proteins are involved in movement along actin filaments, another type of cytoskeletal element, which are prevalent in the synaptic terminal and cell body, but less so as the main track for long-distance axonal transport compared to microtubules.
Therefore, the specific protein responsible for directing the anterograde axonal transport of proteins and membranes along microtubules is Kinesin I.
Important Questions from Cellular communication
Acetylcholine is a potent neurotransmitter, which is released from the neurons. After release they diffuse across the synaptic cleft and combine with nicotinic acetylcholine receptor molecules in the membrane of the postsynaptic cell. The interaction of acetylcholine with the nicotinic acetylcholine receptor produces large transient increase in the permeability of the membrane to specialized ions resulting in signal transduction for nerve impulse. Acetylcholine receptor is a
Column X represents the type of junctions and column Y represents the proteins associated with the junctions.
Column X
Column Y
A.
Anchoring junction
i.
Claudins
B.
Occluding junction
ii.
Delta-Notch
C.
Channel-forming junction
iii.
Desmoglein
D.
Signal-relaying junction
iv.
Connexin
Which one of the following options is a correct match between terms of Columns X and Y?
Bacteria employ various mechanisms to invade or enter host cells, which are either phagocytic or non-phagocytic in nature. Given below are some of the mechanisms which are generally used for carrying out this process.
A. Some bacteria express a protein called invasin that is recognized by host-cell β1 integrins.
B. Actin polymerization along with assembly of clathrin coat results in the internalization of bacteria by zipper mechanism.
C. Some bacteria, including Salmonella enterica, use trigger mechanism to inject a set of effector molecules in the cytosol through type III secretion system.
D. Some bacteria attach to host cell surface receptors inducing local elevation of Ca2+ in cell cytosol, leading to the fusion of lysosomes with bacteria containing plasma membrane vesicles.
Which one of the following represents the combination of correct mechanisms for invading non-phagocytic cells?
In C. elegans, PAR proteins segregate at the cell cortex in the zygote to establish cell polarity. This is dependent on the regulation of the cortical actin cytoskeleton by RhoA. An investigator sought to directly inhibit actin polymerization to analyze the impact of this inhibition on PAR protein localization. Which one of the following chemicals would be the most suitable?
Many signal transduction pathways work as molecular switches. On receiving a signal, they switch from an inactive form to an active form. They return to the inactive form when another signal switches them off. Which of the following processes does NOT directly involve a molecular switch?
