Biology subjects

Martinez-Marquez, J. Y.

Publications and source records attributed to Martinez-Marquez, J. Y..

5 recordsLinked to original sources

bioRxiv2025

The tetraspanin disc proteins, peripherin-2 and ROM1, facilitate CNG channel localization to the rod outer segment

The light-responsive outer segment of rod photoreceptors is composed of two distinct membrane subdomains: discs and the plasma membrane. We investigate how the disc protein peripherin-2 is engaged in CNG channel delivery to the outer segment. Instead of forming outer segments, peripherin-2 knockout (Rds-/-) photoreceptors release ciliary ectosomes, in which CNG channel levels are markedly reduced relative to other outer segment proteins. This is intriguing as downregulation of the CNG channel is not a general feature of degenerative mouse models with dysmorphic outer segments. Overexpression of the {beta}1-subunit of CNG in Rds-/- rods reveals that the majority is trapped in intracellular membranes, but is restored to the outer segment by co-expressing peripherin-2. We test peripherin-2 chimeras containing either the N-terminus, tetraspanin core, or C-terminus and find that the tetraspanin domain is sufficient to localize CNG{beta}1 to the outer segment. We further show that the membrane remodeling function of the tetraspanin domain facilitates this process by the redundant action of the tetraspanin domain from ROM1 and the reemergence of the endogenous CNG channel in aged Rds-/- rods that have produced ciliary membrane protrusions.

cell biology↗

bioRxiv2024

Targeted delivery of rhodopsin's assembled core is required for outer segment extension in mouse rod photoreceptors

Vertebrate vision in dim-light environments is initiated by rod photoreceptor cells that express the photopigment rhodopsin, a G-protein coupled receptor (GPCR). To ensure efficient light capture, rhodopsin is densely packed into hundreds of membrane discs that are tightly stacked within the rod-shaped outer segment compartment. Along with its role in eliciting the visual response, rhodopsin serves as both a building block necessary for proper outer segment formation as well as a trafficking guide for a few outer segment resident membrane proteins. An interesting aspect of rod homeostasis is that mutations that affect the localization of rhodopsin to the outer segment result in photoreceptor degeneration. In this study, we focus on determining the necessary properties of rhodopsins cytosolic C-terminus required for either proper outer segment trafficking and/or the capacity to extend the rudimentary outer segment in rhodopsin knockout (RhoKO) rods. We find that the well-described C-terminal QVAPA outer segment targeting motif also plays a role in endoplasmic reticulum (ER) exit and is necessary for outer segment elongation. Even minor rhodopsin mislocalization prevents efficient outer segment elongation suggesting that QVAPA-targeted delivery of rhodopsin drives outer segment extension. We identify that rhodopsins core, helix-8, and accessible QVAPA targeting motif are the minimal requirements to extend the rudimentary outer segment in RhoKO rods. Our findings provide useful insights into rhodopsins molecular features needed for outer segment delivery and subsequent elongation of this membrane-rich compartment.

cell biology↗

bioRxiv2023

Tectonic Complex Impedes Diffusion through the Ciliary Transition Zone to Ensure Proper Sorting of Membrane Proteins

The primary cilium is a signaling organelle with a unique membrane composition maintained by a diffusional barrier residing at the transition zone. Many transition zone proteins, such as the tectonic complex, are linked to preserving ciliary composition; however, whether these proteins regulate active transport or physically impede membrane diffusion remains unknown. To understand tectonics role, we generated a photoreceptor specific Tctn1 knockout mouse. Loss of Tctn1 resulted in an absence of the entire tectonic complex yet had minimal effects on transition zone structure. Interestingly, we found that protein composition of the photoreceptor cilium was disrupted as non-resident membrane proteins accumulated in the cilium over time, ultimately resulting in photoreceptor degeneration. We further show that membrane proteins moved faster through the transition zone illustrating that the tectonic complex acts as a physical barrier to slow diffusion of membrane proteins so they can be properly sorted by ciliary transport carriers.

cell biology↗

bioRxiv2020

The GARP Domain of the Rod CNG Channel's β1-subunit Contains Distinct Sites for Outer Segment Targeting and Connecting to the Photoreceptor Disc Rim

Vision begins when light is captured by the outer segment organelle of photoreceptor cells in the retina. Outer segments are modified cilia filled with hundreds of flattened disc-shaped membranes. Disc membranes are separated from the surrounding plasma membrane and each membrane type has unique protein components. The mechanisms underlying this protein sorting remain entirely unknown. In this study, we investigated the outer segment delivery of the rod cyclic nucleotide-gated (CNG) channel, which is located in the outer segment plasma membrane where it mediates the electrical response to light. We now show that the targeted delivery of the CNG channel to the outer segment requires pre-assembly of its constituent 1 and {beta}1 subunits and that CNG{beta}1 contains specific targeting information encoded within the glutamic acid-rich region of its N-terminal GARP domain. We also found that the GARP domain connects the CNG channel to photoreceptor disc rims likely through an interaction with peripherin-2 and demonstrated that this function is performed by a proline-enriched region adjacent to the GARP domain. Our data reveal fine functional specializations within the structural domains of the CNG channel and suggest that channel delivery to the outer segment is independent of peripherin-2 interactions. Significance StatementThe precise delivery and organization of signaling proteins in the ciliary outer segment organelle of photoreceptor cells is critical for light detection. We report that the CNG channel, mediating the electrical response to light in rods, contains a region within the N-terminus of its CNG{beta}1 subunit that encodes the outer segment targeting information for the entire channel. This targeting region is adjacent to a region that connects CNG{beta}1 to the rims of photoreceptor discs, likely determining the subcellular compartmentalization of the CNG channel into the outer segment plasma membrane.

cell biology↗

bioRxiv2018

Developing Future Biologists: creating and assessing a portable short course to engage underrepresented undergraduate students in developmental biology

Many barriers discourage underrepresented students from pursuing science careers. To access graduate education, undergraduate students must first gain exposure to a particular subject and subsequently accumulate related coursework and research experience. Many underrepresented students lack exposure to developmental biology due to limited undergraduate course offerings and finite resources at smaller institutions. To address this disparity, a group of University of Michigan graduate students and postdoctoral fellows created a portable short course focusing on developmental biology, titled \"Developing Future Biologists\" (DFB). This weeklong educational initiative provides hands-on laboratory sessions, interactive lectures, and professional development workshops to teach students about developmental biology and increase awareness of scientific career options. To evaluate course effectiveness, we developed a pre-post assessment, incorporating main ideas from the BioCore Guide. Student understanding of basic concepts and perceived experience in developmental biology increased in DFB participants, despite the abbreviated nature of the course. Here, we provide all course materials and an in-depth analysis of the assessment we created. The DFB portable short course model is an easily adaptable tool that connects undergraduate students with opportunities for advanced study and lowers barriers for underrepresented students in science, technology, engineering, and mathematics.

scientific communication and education↗